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HP 8711A User's Manual

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1. Both types of transfers are utilized with different interfaces and both will be fully described as necessary Additional Interface Functions Another powerful feature of some interfaces is to relieve the computer of low level tasks such as performing data transfer handshakes This distribution of tasks eases some of the computer s burden and also decreases the otherwise stringent response time requirements of external devices The actual tasks performed by each type of interface vary widely and are described in the next section of this chapter interfacing Concepts 2 3 Interface Overview Now that you see the need for interfaces you should see what kinds of interfaces are available for the computer Each of these interfaces is specifically designed for specific methods of data transfer each interface s hardware configuration reflects its function The HP IB Interface This interface is Hewlett Packard s implementation of the IEEE 488 1978 Standard Digital Interface for Programmable Instrumentation The acronym HP IB comes from Hewlett Packard Interface Bus often called the bus Handshake HP IB interface Data and Control Shielded Cable to Device s Hardware and Firmware Backplane Connectors 25 Pin Connector Logic and Shield Grounds Block Diagram of the HP IB Interface The HP IB interface fulfills all four compatibility requirements hardware
2. Enter the first two bytes as an INTEGER then the rest as string data ENTER Device USING W K N N Terminating Enters that Use Images This section describes the default statement termination conditions for enters that use images for devices The effects of numeric item and string item terminators and the end or identify EOI signal during these operations are discussed in this section After reading this section you will be able to better understand how enters that use images work and how the default statement termination conditions are modified by the and image specifiers Default Termination Conditions The default statement termination conditions for enters that use images are very similar to those required to terminate free field enters Either of the following conditions will properly terminate an ENTER statement that uses an image An END indication such as the EOI signal or end of data is received with the byte that satisfies the last image item within 256 bytes after the byte that satisfied the last image item w A line feed is received as the byte that satisfies the last image item exceptions are the B and W specifiers or within 256 bytes after the byte that satisfied the last image item EO Redefinition It is important to realize that when an enter uses an image when the secondary keyword USING is specified the definition of the EOI signal is automatically modified If the EOI sign
3. when they terminate the entry The EOI signal also terminates entry into a string variable but the variable must be the last item in the destination list during free field enters All characters received from the source are entered directly iemph appropriate string variable until any of the following conditions occurs m An item terminator character is received m The number of characters entered equals the dimensioned length of the string variable m The EOI signal is received The following statements and resultant variable contents illustrate the first two conditions the next section describes termination by EOI Assume that the string variables Five char and Ten char are dimensioned to lengths of 5 and 10 characters respectively Entering Data 5 5 ENTER Device Five_char Consumed pm eee Spee eles te crec done cir ea n Five_char ignored Terminator for both item and statement The variable Five_char only receives the characters ABCDE but the characters FGH are entered and ignored in search of the terminating carriage return line feed or line feed ENTER Device Ten_char Consumed Consumed por n m alefe o e e e w e a ejcjo e r o cn tr Nonas rc y a Ten char Terminator Ten_char Terminator for both item for both item and statement and statement The result of entering the preceding data with the given ENTER statement is that Ten_char receives the characters ABCDEFG and the
4. instead they are treated as string characters and placed in the variable Receiving an END indication terminates the image item for instance receiving EOI with a character on an HP IB interface encountering an end of data or reaching the variable s dimensioned length These specifiers are ignored for ENTER operations however they are allowed for compatibility with OUTPUT statements that is so that one image may be used for both ENTER and OUTPUT statements Note that it may be necessary to skip characters with specifiers such as X or when ENTERing data that has been sent by including these specifiers in an OUTPUT statement Examples of String images Enter 10 characters ENTER Device USING 10A Ten_chars Enter using the free field rules ENTER Device USING K Any_string Enter two strings ENTER Device USING 5A K String Number Enter a string and a number ENTER Device USING 5A K String Number Enter characters until string is full or END is received ENTER Device USING X A11l_chars 5 12 Entering Data ignoring Characters These specifiers are used when one or more characters are to be ignored i e entered but not placed into a string variable Specifiers Used to Ignore Characters Image Specifier Meaning _ X Specifies that a character is to be entered but ignored not placed into a variable literal Specifies that the number of characters in the literal are to b
5. 2 35 faye sJolel fo aloe sequence OUTPUT Device USING D 2 6 i EMI sed n OUTPUT Device USING DRDD 3 1416 3 BE EOL Sequence OUTPUT Device USING H 3 1416 EBDDOUHN W Sequence Outputting Data 4 11 String Images These types of image specifiers are used to specify the format of string data items A literal K K a String Examples Image Specifier Meaning Character Specifiers Specifies that one character is to be output Trailing spaces are used as fill characters if the string contains less than the number of characters specified All characters placed in quotes form a string literal which is output exactly as is Literals can be placed in output images which are part of OUTPUT statements by enclosing them in double quotes Specifies that the string is to be output in compact format similar to the standard string format however no item terminators are output as with the standard string format OUTPUT Device USING 8A Characters eee sequence OUTPUT Device USING K Literal AB rural sequence OUTPUT Device USING K Hello m z sequence OUTPUT Device USING SA Hello EOL sequence 4 12 Outputting Data Binary Images These image specifiers are used to output bytes 8 bit data and words 16 bit data to the destination Typical uses are to output non ASCIT characters or integers in their internal representation Binary Specifie
6. Data mu EOL EOL sequence sequence OUTPUT Device USING K Data HESS OUTPUT Device USING B 12 OUTPUT Device USING K Data BENE Outputting Data 4 15 OUTPUT Device USING L K Data PERDO Je fur sequence Additional Image Features Several additional features of outputs that use images are available with the computer Several of these features which have already been shown will be explained here in detail Repeat Factors Many of the specifiers can be repeated without having to explicitly list the specifier as many times as it is to be repeated For instance to a character field of 15 characters you do not need to use AAAAAAAAAAAAAAA instead you merely specify the number of times that the specifier is to be repeated in front of the image 15A The following specifiers can be repeated by specifying an integer repeat factor the specifiers not listed cannot be repeated in this manner Repeatable Specifiers Nonrepeatable Specifiers Z D A X L S M R E K H B W Y Examples OUTPUT Device USING 4Z 3D 328 03 Se Pleo sequence OUTPUT Device USING 64 Data bytes t EOL sequence OUTPUT Device USING 5X 24 Data DE sequence 4 18 Qutputting Data OUTPUT Device USING 2L 44A Data ECL sequence OUTPUT Device USING BA 20 The End sequence OUTPUT Device USING 2 sequence image Re Use If
7. These advantages fall in the following areas m execution speed a redirecting data to or from other destinations m access to mass storage files m attribute control Execution Speed When a device selector is used in an I O statement to specify the I O path to a device first the numeric expression must be evaluated then the corresponding attributes of the I O path must be determined before the I O path can be used If an I O path name is specified in an OUTPUT or ENTER statement all of this information has already been determined at the time the I O path name was assigned Thus an I O statement containing an I O path name executes slightly faster than using the corresponding I O statement containing a device selector for the same set of source list expressions 3 6 Directing Data Flow Redirecting Data Using numeric variable device selectors as with I O path names allows a single statement to be used to move data between the computer and several devices Simple examples of redirecting data in this manner are shown in the following programs Example of Re Directing with Device Selectors 100 Device i 110 GOSUB Data_out 200 Device 701 210 GOSUB Data_out 410 Data_out OUTPUT Device Data 420 RETURN Example of Re Directing with I O Path Names 100 ASSIGN Device TO 1 110 GOSUB Data_out 200 ASSIGN Device TO 9 210 GOSUB Data out 410 Data_out OUTPUT Device Data 420 RETURN The preceding two methods of redirecti
8. amp vou 4A Ee ee SR Nested Images Example a uh ae ae ea ee I O Path Attributes The FORMAT Attributes Assigning Default FORMAT Attributes Specifying I O Path Attributes Changing the EOL Sequence Attribute Restoring the Default Attributes Concepts of Unified I O Data Representation Design Criteria Mela faina 1 O Patbe Lo Files o e o9 a PILL SLI BDAT HPUX and DOS Files ASCH Files Data Representation Summary Applications of Unified I O 1 O Operations with String Variables Outputting Data to String Variables Bxample so 322 da l ET Example ere xk So lE le e ca Entering Data From String Variables IS E 5 1 ww dod i4 0 c9 ho 4 O 7 O 9 0 0 9 9 ct 5 c t t9 8 e s amp x 4 8 s gt 4 s s gt 8 LL gt 7 s 0 58 a a a amp 8 9 e a a AE s s e e o 8 5 a e a Wie a e r 2 0 5 a 8 s sk LE 0 8 s s 8 y t o ZZ LL CL gt 8 8 t 8 8 5 8 4 gt a 9 s o s 0 9 a 4 e 4 y t s s E SI s 0c 5 5 Li gt 8 c 9 095 dA 5 2 5 1 5 2 9 5 5 7 5 7 5 8 5 9 5 9
9. spaces end of line sequences and form feed characters Speciai Character Specifiers Specifies that a space character CHR 32 is to be output Special Character Examples Specifies that a carriage return character CHR 13 and a line feed character CHR 10 are to be output Specifies that a form feed character CHR 12 is to be output OUTPUT Device USING A 4X A M A M A EOL sequence OUTPUT Device USING 50X 50 spaces sequence OUTPUT GDevice USING sequence OUTPUT Device USING sequence 4 14 Qutputting Data Termination Images These specifiers are used to output or suppress the end of line sequence output after the last data item Termination Specifiers Image Specifier Meaning L Specifies that the current end of line sequence is to be output The default EOL characters are CR and LF see Changing the EOL Sequence for details on how to redefine these characters Specifies that the EOL sequence that normally follows the last item is to be suppressed Is ignored in output images but is allowed to be compatible with ENTER images Specifies that the EOL sequence that normally follows the last item is to be replaced by a single carriage return character CR Specifies that the EOL sequence that normally follows the last item is to be replaced by a single line feed character LF Termination Examples OUTPUT Device USING 4A L
10. the last item in the destination list 2 Trailing non numerics terminate entry into a numeric variable and the terminating characters of both string and numeric items are consumed In this manual consumed characters refers to characters used to terminate an item but not entered into the variable ignored characters are entered but are not used ENTER Device Real_number String Consumed Consumed par ema n u m o e e 213 lalale elo For enano A E __TOOE__ ae gtet sd ignored Real_number Numeric String Terminator item for both item terminator and statement The result of entering the preceding data with the given ENTER statement is that Real_number receives the value 123 4 and String receives the characters BCD The A was lost when it terminated the numeric item the string item terminator s are also lost The string item terminator s also terminate the ENTER statement since String is the last item in the destination list 3 If more than 16 digits are received only the first 16 are used as significant digits However all additional digits are treated as trailing zeros so that the exponent is built correctly Entering Data 5 3 ENTER GDevice Real number 1 Consumed pm ifafsp sfef7fafofolif 3f s sfcr A ud Real number 1 Terminator for both item and statement The result of entering the preceding data with the given ENTER statement is that Real_nu
11. 2 Interfacing Concepts before reading about general or interface specific techniques Experienced may decide to go directly to the chapter in your instrument specific manual programmers that describes the particular interface to be used It is also usually helpful to become familiar with display and keyboard I O operations since these are helpful in seeing results while testing I O programs If you need more background as you read about a particular topic consult chapters 3 through 6 for a detailed explanation The brief descriptions in the next section will help you determine which chapters you will need to read for your particular application Manual Overview 1 1 Chapter Previews This manual is intended to provide background and tutorial information for programmers who have not written HP Instrument BASIC I O programs before It presents topics and programming techniques applicable to all interfaces Chapter 2 Interfacing Concepts This chapter presents a brief explanation of relevant interfacing concepts and terminology This discussion is especially useful for beginners as it covers much of the why and how of interfacing Experienced programmers may also want to review this material to better understand the terminology used in this manual Chapter 3 Directing Data Flow This chapter describes how to specify which instrument resource is to send data to or receive data The use of device selectors string var
12. 4 13 Images ENTER 4 15 Images nested 4 18 Images numeric 4 9 Images Outputs that Use 4 7 Images Special Character 4 14 Images string 4 12 Images Terminating Enters that Use 5 14 Input 2 1 Interface Functions Additional 2 3 Interface primary function of an 2 2 Interfaces select codes 3 2 Interfacing Concepts 2 1 1 0 2 1 I O Applications of Unified 6 7 I O Concepts of Unified 6 4 I O Operations with String Variables 6 7 I O Path Attributes 6 1 I O Path Attributes Specifying 6 3 1 O Path Benefits 3 6 1 O path name 3 3 6 1 I O Path Names Closing 3 4 I O Path Names Re Assigning 3 3 I O paths 3 3 I O Paths to Files 6 5 I O Process 2 8 I O Statements and Parameters 2 8 Item Separators 4 2 5 1 Item Terminators 4 2 5 2 Manual Organization 1 1 Mechanical Compatibility Electrical and 2 2 Modifiers Statement Termination 5 15 N Names string variable 3 1 Nested Images 4 18 5 17 Non Repeatable Specifiers 5 16 Number builder 5 2 Numbers Representing 2 7 Numeric Format Standard 4 1 Numeric Images 4 9 5 11 Numeric specifier 5 11 o Output 2 1 OUTPUT statement 2 8 3 1 4 1 5 1 Outputs that Use Images 4 7 Outputting Data 4 1 OUTPUT USING statement 4 7 Index 2 p Previews Chapter 1 2 Primary address 3 2 Primary function of an interface 2 2 R Radix specifier 4 9 Re Assigning I O Path Names 3 3 Re Directing Data 3 7 Repeatable
13. The maximum number of levels of nesting is eight Example ENTER Source USING 2 B 5A N1 N1 N2 N2 Entering Data 5 17 I O Path Attributes This chapter contains two major topics both of which involve additional features provided by I O path names m The first topic is that I O path names can be given attributes which control the way that the system handles the data sent and received through the I O path Attributes are available for such purposes as controlling data representations and defining special end of line EOL sequences amp The second topic is that one set of I O statements can access most system resources instead of using a separate set of statements to access each class of resources This second topic herein called unified I O may be considered an implicit attribute of I O path names The FORMAT Attributes All I O paths possess one of the two following attributes a FORMAT ON means that the data are sent in ASCII representation w FORMAT OFF means that the data are sent in BASIC internal representation Before getting into how to assign these attributes to I O paths let s take a brief look at each one With FORMAT ON internally represented numeric data must be formatted into its ASCII representation before being sent to the device Conversely numeric data being received from the device must be unformatted back into its internal representation These operations are shown in th
14. any of the above data streams with the given ENTER statement is that Number receives the value 12345 If the EOI signal accompanies a numeric character it is entered and used to build the number if the EOI is received with a numeric terminator the terminator 1s lost as usual ENTER Device Number String An error is reported Error 153 insufficient data for ENTER Sona amnem n a Number Sent with EOI The result of entering the preceding data with the given statement is that an error is reported when the character 5 accompanied by EOI is received However Number receives the value 12345 but String retains its previous value An error is reported because all variables in the destination list have not been satisfied when the EOI is received Thus the EOI signal is an immediate statement terminator during free field enters The EOI signal has a different definition during enters that use images as described later in this chapter Enters that Use Images The free field form of the ENTER statement is very convenient to use the computer automatically takes care of placing each character into the proper destination item However there are times when you need to design your own images that match the format of the data output by sources Several instances for which you may need to use this type of enter operations are the incoming data does not contain any terminators the data stream is not followed by an end of line seque
15. discussed in the I O Path Attributes chapter Directing Data Flow 3 7 Outputting Data Introduction This chapter describes the topic of outputting data to devices outputting data to string variables and mass storage files is described in the I O Path Attributes chapter of this manual in Data Storage and Retrieval chapter 7 of HP Instrument BASIC Programming Techniques There are two general types of output operations The first type known as free field outputs use the HP Instrument BASIC s default data representations The second type provides precise control over each character sent to a device by allowing you to specify the exact image of the ASCII data to be output Free Field Outputs Free field outputs are invoked when the following types of OUTPUT statements are executed Examples OUTPUT GDevice 3 14 Radius 2 OUTPUT Printer String data Num_1 OUTPUT 9 Test Score Student OUTPUT Escape_code CHR 27 2 24185 The Free Field Convention The term free field refers to the number of characters used to represent a data item During free field outputs HP Instrument BASIC does not send a constant number of ASCII characters for each type of data item as is done during fixed field outputs which use images described later Instead a special set of rules is used that govern the number and type of characters sent for each source item The rules used for
16. electrical data and timing with no additional modification Just about all you need to do is connect the interface cable to the desired HP IB device and begin programming All resources connected to the computer through the HP IB interface must adhere to this IEEE standard The bus is somewhat of an independent entity it is a communication arbitrator that provides an organized protocol for communications between several devices The bus can be configured in several ways The devices on the bus can be configured to act as senders or receivers of data and control messages depending on their capabilities 2 4 Interfacing Concepts The RS 232C Serial Interface The serial interface changes 8 bit parallel data into bit serial information and transmits the data through a two wire usually shielded cable data is received in this serial format and is converted back to parallel data This use of two wires makes it more economical to transmit data over long distances than to use 8 individual lines Parallel Paroitett qum Serial Converter UART Backplane Connectors interface Hardware Special Purpose Block Diagram of the Serial Interface Bit Serial 25 Pin Connector Shieided Cable to a Device Data is transmitted at several programmable rates using either a simple data handshake or no handshake at all The main use of this interface is in communicating with sim
17. maximize the rate at which the computer can move the data between its resources amp to minimize the amount of storage space required to store a given amount of data w to be compatible with the data representation used by the resources with which the computer is to communicate The internal representations implemented in the computer are designed according to the first three of the above criteria However the last criterion must always be met if communication is to be achieved If the resource uses the ASCII representation this compatibility requirement takes precedence over the other design criteria The ASCH representation fulfills this last criterion for most devices and for the computer operator The first three criteria are further discussed in the following description of data representations used for mass storage files 6 4 1 0 Path Attributes I O Paths to Files There are three types of data files ASCII BDAT and HP UX or DOS Only the ASCII data representation is used with ASCII files but either the ASCII FORMAT ON or the internal FORMAT OFF representation can be used with BDAT and HP UX or DOS files BDAT HPUX and DOS Files BDAT HP UX and DOS files have been designed to maximize the efficiency with which HP Instrument BASIC moves stores and manipulates data Both numeric and string computations are much faster These internal data representations allow much more data to be stored on a disc because there is no storage ove
18. of a carriage return and line feed CR LF sent with no device dependent END indication It is also possible to define your own special EOL sequences that include sending special characters and sending an END indication In order to define non default EOL sequences to be sent by the OUTPUT statement an I O path must be used The EOL sequence is specified in one of the ASSIGN statements that describe the I O path An example is as follows ASSIGN Device TO 7 EOL CHR 10 amp CHR 10 amp CHR 13 The characters following EOL are the new EOL sequence characters Any character in the range CHR 0 through CHR 255 may be included in the string expression that defines the EOL characters however the length of the sequence is limited to eight characters or less 4 4 QOutputting Data If END is included in the EOL attribute an interface dependent END indication is sent with or after the last character of the EOL sequence However if no EOL sequence is sent the END indication is also suppressed The following statement shows an example of defining the EOL sequence to include an END indication ASSIGN Device TO 7 EOL CHR 13 amp CHR 10 END With the HP IB Interface the END indication is an End or Identify message EOI sent with the last EOL character The default EOL sequence is a CR and LF sent with no END indication this default can be restored by assigning EOL OFF to the I O path EOL sequences can also be sent by usi
19. or The default exponent is a four character sequence consisting of an E the exponent sign and two exponent digits equivalent to an ESZZ image Since the number is left justified in the specified digit field the image for a negative number must contain a sign specifier see the next section ESZ Same as E but only 1 exponent digit is output ESZZZ Same as E but three exponent digits are output Specifies that the number is to be output in a compact format similar to the standard numeric format however neither leading spaces that would otherwise replace a sign nor item terminators commas are output as would be with the standard numeric format Like K except that the number is to be output using a comma radix European radix Outputting Data 4 9 Numeric Examples OUTPUT Device USING DDDD 123 769 sequence OUTPUT Device USING 4D 1 2 EOL sequence OUTPUT Device USING ZZ DD 1 675 EOL sequence OUTPUT Device USING Z D 35 x EOL sequence OUTPUT Device USING DD E 12345 VEE bee sequence OUTPUT Device USING 2D DDE 2E 4 apra sequence OUTPUT Device USING K 12 400 a tes sequence OUTPUT CRT USING MDD 2D 12 449 EE EE a sequence 4 10 Outputting Data OUTPUT CRT USING MDD DD 2 09 sequence OUTPUT 1 USING SD D 2 449 2 4 EOL sequence 25 OUTPUT 1 USING SZ DD 49 DEBDUROM sequence OUTPUT CRT USING SDD DDE
20. specifier 4 16 5 16 Repeat Factors 5 16 Repeat Factors Image 4 16 Resource specifying a 3 1 RS 232C Serial Interface 2 5 S Select codes of built in interfaces 3 2 Selectors Device 3 2 Selectors HP IB Device 3 2 Semicolon separator 4 3 Separator Comma 4 2 Separator semicolon 4 3 Serial Interface RS 232C 2 5 Sign specifier 4 9 Special Character Images 4 14 Specifiers Binary 4 13 Character 4 12 Digit 4 9 Exponent 4 9 Numeric 5 11 Radix 4 9 Repeatable 4 16 Sign 4 9 Special Character 4 14 Termination 4 15 Specifying an I O resource 3 1 Speed Execution 3 6 Statement Termination Modifiers 5 15 String Data Entering 5 5 String Format Standard 4 2 String images 4 12 5 12 String variable names 3 1 String Variables Entering Data From 6 9 String Variables Outputting Data to 6 7 T Terminating Enters that Use Images 5 14 Termination Conditions Default 5 14 Termination specifier 4 15 Terminology 2 1 Timing Compatibility 2 3 U Unified I O 6 7
21. terminating LF or CR LF is lost 5 6 Entering Data Terminating Free Field ENTER Statements Terminating conditions for free field ENTER statements are as follows 1 If the last item is terminated by a line feed or by a character accompanied by EOI the entire statement is properly terminated 2 Han END indication is received while entering data into the last item the statement is properly terminated Examples of END indications are encountering the last character of a string variable while entering data from the variable and receiving EOI with a character 3 If one of the preceding statement termination conditions has not occurred but entry into the last item has been terminated up to 256 additional characters are entered in search of a termination condition If one is not found an error occurs One case in which this termination condition may not be obvious can occur while entering string data If the last variable in the destination list is a string and the dimensioned length string has been reached before a terminator is received additional characters are entered but ignored until the terminator is found The reason for this action is that the next characters received are still part of this data item as far as the data sender is concerned These characters are accepted from the sender so that the next enter operation will not receive these leftover characters Another case involving numeric data can also occur See the e
22. that a variable number of characters are to be entered and interpreted according to the rules of the number builder same rules as used in free field ENTER operations H H Like K except that a comma is used as the radix indicator and a period is used as the terminator for the numeric item Examples of Numeric Images These 5 are equivalent ENTER Device USING SDD D Number ENTER Device USING 3D D Number ENTER Device USING 5D Number ENTER Device USING DESZZ Number ENTER Device USING x DD Number Use the rules of the number builder ENTER Device USING K Number Entering Data 5 11 Enter five characters using comma as radix ENTER Device USING DDRDD Number Use the rules of the number builder but use the comma as radix ENTER Device USING H Humber String Images The following specifiers are used to determine the number of and the interpretation of data bytes entered into string variables Sting Specifiers Image Specifier Specifies that one byte is to be entered and interpreted as a string character Any terminators are entered into the string when this specifter 1s used Specifies that free field ENTER conventions are to be used to enter data into a string variable characters are entered directly into the variable until a terminating condition is sensed such as CR LF LF or an END indication Like K except that line feeds LF s do not terminate entry into the string
23. the data initially output to the variable by the first OUTPUT statement The string variable s length header 4 bytes is updated and compared to the dimensioned length of the string as characters are output to the variable I the string is filled before all items have been output an error is reported however the string contains the first n characters output where n is the dimensioned length of the string Example The following program outputs string and numeric data items to a string variable and then calls a subprogram that displays each character its decimal code and its position within the variable 100 ASSIGN Crt TO 1 CRT is disp device 110 120 OUTPUT Str_var 12 AB 34 130 5 140 CALL Read string Crt Str_var 150 160 END 170 180 t 190 SUB Read_string fDisp Str_var 200 210 Table heading 220 OUTPUT Disp a m a a aae aet sae t ua sae sae mat i iet wae 230 OUTPUT G Disp Character Code Pos 240 OUTPUT 6Disp muse memet 250 Dsp_img 2X 4A 5X 3D 2X 3D 260 270 Now read the string s contents 280 FOR Str_pos 1 TO LEN Str_var 290 Code NUM Str_var Str_pos 1 300 IF Code lt 32 THEN Don t disp CTRL chars 310 Char z CTRL 320 ELSE 330 Char sStr var Str pos 1 Disp char 340 END IF 350 1 360 OUTPUT Disp USING Dsp img Char Code Str pos 370 NEXT Str_pos 380 t 390 Finish table 400 OUTPUT 6Disp 410 OUTPUT Disp Bl
24. the number of items in the source list exceeds the number of matching specifiers in the image list the computer attempts to reuse the image s beginning with the first image 110 ASSIGN Device TO CRT 120 Num_i i 130 Num 2 2 140 i 150 OUTPUT Device USING K Num_1 Data_1i Num_2 Data_2 160 OUTPUT Device USING K KFum_i Data_i Num_2 Data_2 170 END Resultant Display iData_12Data_2 1 Data_1 2 Data_2 Since the K specifier can be used with both numeric and string data the above OUTPUT statements can reuse the image list for all items in the source list If any item cannot be output using the corresponding image item an error results In the following example Error 100 in 150 occurs due to data mismatch 110 ASSIGN Device TO CRT 120 Num i i 130 Num_2 2 140 i 150 OUTPUT Device USING DD DD Num_1 Num_2 Data_1 160 END Outputting Data 4 17 Nested Images Another convenient capability of images is that they can be nested within parentheses The entire image list within the parentheses will be used the number of times specified by the repeat factor preceding the first parenthesis The following program is an example of this feature 100 ASSIGN Device TO 701 110 120 OUTPUT Device USING 3 B X DD X DD 65 66 67 68 69 30 END Resultant Output aleje efe elo facts sequence This nesting with parentheses is made with the same hierarchy as with parenthetical nesting within math
25. 5 9 5 10 9 11 5 11 5 12 5 12 5 13 5 13 5 13 5 14 5 14 5 14 5 14 5 15 9 16 5 16 9 16 5 16 5 16 5 17 5 17 6 1 E 6 2 6 3 6 3 6 4 6 4 6 4 6 5 6 5 6 6 6 7 6 7 6 7 6 7 6 8 6 9 6 9 Contents 3 Example s s cv La e A A e DA E e a 6 10 Example sce wu ov e A DE asa 60810 Index Contents 4 Manual Overview Introduction This manual presents the concepts of computer interfacing that are relevant to programming in HP Instrument BASIC Note that not all features described in this manual may be implemented on your instrument Please consult your instrument specific manual for a description of implemented features The topics presented herein will increase your understanding of interfacing the host instrument and external devices and computers with HP Instrument BASIC programs Manual Organization This manual is organized by topics and is designed as a learning tool not a reference The text is arranged to focus your attention on interfacing concepts rather than to present only a serial list of the HP Instrument BASIC language I O statements Once you have read this manual and are familiar with the general and specific concepts involved you can use either this manual or the HP Instrument BASIC Language Reference when searching for a particular detail of how a statement works This manual is designed for easy access by both experienced programmers and beginners Beginners may want to begin with Chapter
26. A Ah A images Images are used to specify the format of data during I O operations Each image consists of groups of individual image or field specifiers such as 6A SDDD DDD and 3X in the preceding examples Each of these field specifiers describe one of the following things w It describes the desired format of one item in the source list For example 6A specifies that a string item is to be output in a 6 character Alpha field SDDD DDD specifies that a numeric item is to be output with Sign 3 Decimal digits preceding the decimal point followed by 3 Decimal digits following the decimal point a It specifies that special character s are to be output For example 3X specifies that 3 spaces are to be output There is no corresponding item in the source list Thus you can think of the image list as either a precise format description or as a procedure It is convenient to talk about the image list as a procedure for the purpose of explaining how this type of OUTPUT statement is executed Again each image list consists of images that each describe the format of data item to be output The order of images in the list corresponds to the order of data items in the source list In addition image specifiers can be added to output or to suppress the output of certain characters Example of Using an Image We will use the first of the four equivalent output statements shown above Don t worry if you don t und
27. HP Instrument BASIC User s Handbook HP 8711A RF Network Analyzer PD Packar HP Part No 08711 90112 Printed in USA July 1993 Notice The information contained in this document is subject to change without notice Hewlett Packard makes no warranty of any kind with regard to this material including but not limited to the implied warranties of merchantability and fitness for a particular purpose Hewlett Packard shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing performance or use of this material Copyright Hewlett Packard Company 1992 1993 All Rights Reserved Reproduction adaptation or translation without prior written permission is prohibited except as allowed under the copyright laws 1400 Fountaingrove Parkway Santa Rosa CA 95403 1799 USA Contents 1 Manual Overview Introduction Manual rgaitisadioni Chapter Previews Chapter 2 Interfacing Contents Chapter 3 Directing Data Flow Chapter 4 Outputting Data Chapter 5 Entering Data Chapter 6 I O Path Attributes Specific Interfaces Interfacing Concepts Terminology Why Do You Need an pueda Electrical and Mechanical Compatibility i Data Compatibility Timing Compatibility Additional Interface Functions Interface Overview The HP IB Interface da The RS 232C Serial Interface Data Representations Bits and Bytes Representing Numbers Representing Ch
28. O operations with string variables The second application involves using a disc file to simulate a device 1 0 Operations with String Variables This section describes both the details of and several uses of outputting data to and entering data from string variables Outputting Data to String Variables When a string variable is specified as the destination of data in an OUTPUT statement source items are evaluated individually and placed into the variable according to the free field rules or the specified image depending on which type of OUTPUT statement is used Thus item terminators may or may not be placed into the variable The ASCII data representation is always used during outputs to string variables Characters are always placed into the variable beginning at the first position no other position can be specified as the beginning position at which data will be placed Thus random access of the information in string variables is not allowed from OUTPUT and ENTER statements all data must be accessed serially For instance if the characters 1234 are output to a string variable by one OUTPUT statement and a subsequent OUTPUT statement outputs the characters 5678 to the same variable the second output does not begin where the first one left off i e at string position five The second OUTPUT 1 0 Path Attributes 6 7 statement begins placing characters in position one just as the first OUTPUT statement did overwriting
29. SIGN Device Restores ALL default attributes Concepts of Unified 1 0 The HP Instrument BASIC language provides the ability to communicate with the several system resources with the OUTPUT and ENTER statements The next section of this chapter describes how data can be moved to and from string variables with OUTPUT and ENTER statements And if you have read about mass storage operations in the Data Storage and Retrieval chapter of HP Instrument BASIC Programming Techniques you know that the ENTER and OUTPUT statements are also used to move data between the computer and mass storage files This ability to move data between the computer and all of its resources with the same statements is a very powerful capability of the HP Instrument BASIC language Before briefly discussing I O paths to mass storage files the following discussion will present some background information that will help you understand the rationale behind implementing the two data representations used by the computer The remainder of this chapter then presents several uses of this language structure Data Representation Design Criteria As you know the computer supports two general data representations the ASCII and the internal representations This discussion presents the rationale of their design The data representations used by the computer were chosen according to the following criteria amp to maximize the rate at which computations can be made to
30. T 1 STR Str Num Num 240 l QUTPUT 1 250 OFF ERROR The next one will work 260 270 ENTER String USING 3A4 3D Str Num 280 OUTPUT i Second try results 290 OUTPUT 1 Str Str Num Num 300 310 END This technique is convenient when attempting to enter an unknown amount of data or when numeric and string items within incoming data are not terminated The data can be entered into a string variable and then searched by using images Example ENTERs from string variables can also be used to generate a number from ASCII numeric characters a recognizable collection of decimal digits decimal point and exponent information rather than using the VAL function As with outputs to string variables images can be used to interpret the data being entered 30 Number Value 43 5879E 13 40 50 ENTER Number Value 60 PRINT VALUE Value 70 END 6 10 1 0 Path Attributes A Additional Interface Functions 2 3 Address primary 3 2 ASCII Files 6 6 ASSIGN statement 3 3 4 6 2 Attribute control 3 7 Attributes EOL Sequence 6 3 Attributes FORMAT 6 1 Attributes I O Path 6 1 Attributes Restoring the Default 6 4 B Backplane computer 2 2 BDAT Files 6 5 Binary images 4 13 Binary Images 5 13 Binary specifier 4 13 Bits and Bytes 2 6 Bus 2 1 e Chapter Previews 1 2 Characters Ignoring 5 13 Character specifier 4 12 Characters Representing 2 7 Closing I O Path Names 3 4 Co
31. TPUT Device END Neither EOL sequence nor EOI is sent since no data is sent Outputs that Use Images The free field form of the OUTPUT statement is very convenient to use However there may be times when the data output by the free field convention is not compatible with the data required by the receiving device Several instances for which you might need to format outputs are special control characters are to be output the EOL sequence carriage return and line feed needs to be suppressed or the exponent of a number must have only one digit This section shows you how to use image specifiers to create your own unique data representations for output operations The OUTPUT USING Statement When this form of the OUTPUT statement is used the data is output according to the format image referenced by the USING secondary keyword This image consists of one or more individual image specifiers that describe the type and number of data bytes or words to be output The image can be either a string literal a string variable or the line label or number of an IMAGE statement Examples of these four possibilities are listed below 100 OUTPUT 1 USING 6A SDDD DDD 3X K 123 45 100 Image_str 6A SDDD DDD 3X 110 OUTPUT CRT USING Image str K 123 45 100 OUTPUT CRT USING Image stmt K 3123 45 110 Image stmt IMAGE 6A SDDD DDD 3X 100 OUTPUT 1 USING 110 K 123 45 110 IMAGE 64 SDDD DDD 3X 4 6 Outputting Data AA
32. a s fe 3 0 7 fur Evaluates to 1 234E 309 cicca sensei q aa The resultant value Terminator cannot be stored for both items in Real number and statement The data is entered but evaluates to a number outside the range of REAL numbers Consequently error 19 is reported and the variable Real_number retains its former value 6 If the item is the last one in the list both the item and the statement need to be properly terminated If the numeric item is terminated by a non numeric character the statement will not be terminated until it either receives a line feed character or an END indication such as EOI signal with a character The topic of terminating free field ENTER statements is described later Entering String Data Strings are groups of ASCII characters of varying lengths Unlike numbers almost any character can appear in any position within a string there is not really any defined structure of string data The routine used to enter string data is therefore much simpler than the number builder It only needs to keep track of the dimensioned length of the string variable and look for string item terminators such as CR LF LF or EOI sent with a character String item terminator characters are either a line feed LF or a carriage return followed by a line feed CR LF As with numeric item terminators characters these characters are not entered into the string variable during free field enters they are lost
33. al terminates the last image item the entire statement is properly terminated as with free field enters In addition multiple EOI signals are now allowed and act as item terminators however the EOI must be received with the byte that satisfies each image item If the EOI is received before any image is satisfied it is ignored Thus all images must be satisfied and EOI will not cause early termination of the ENTER USING image statement The following table summarizes the definitions of EOI during several types of ENTER statement The statement terminator modifiers are more fully described in the next section 5 14 Entering Data Definition of EOI Effects of EO During ENTER Statements Free Field ENTER ENTER USING Statements without it or Y Immediate Item terminator Item terminator Immediate statement or statement or statement statement terminator terminator terminator terminator Statement Terminator Required Early Termination Allowed Statement Termination Modifiers These specifiers modify the conditions that terminate enters that use images The first one of these specifiers encountered in the image list modifies the termination conditions for the ENTER statement If another of these specifiers is encountered in the image list it again modifies the terminating conditions for the statement Image Specifier Statement Termination Modifiers Meaning Specifies that a statement termination condition is not requi
34. and how both statements will use the image Example of an Enter Using an Image This example is used to show you exactly how the computer uses the image to enter incoming data into variables Look through the example to get a general feel for how these enter operations work Afterwards you should read the descriptions of the pertinent specifier s Assume that the following stream of data bytes are to be entered into the computer Ignored Degrees Units ignored Assume EO is sent with this character Entering Data 5 9 Given the preceding conditions let s look at how the computer executes the following ENTER statement that uses the specified IMAGE statement 300 ENTER Device USING Image_1 Degrees Units 310 Image 1 IMAGE 8X SDDD D A Step 1 Step 2 Step 3 Step 4 Step 5 The computer evaluates the first image of the IMAGE statement It is a special image in that it does not correspond to a variable in the destination list It specifies that eight characters of the incoming data stream are to be ignored Eight characters Temp are entered and are ignored i e are not entered into any variable The computer evaluates the next image It specifies that the next six characters are to be used to build a number Even though the order of the sign digit and radix are explicitly stated in the image the actual order of these characters in the incoming data stream does not have to match this specifier e
35. ank line 420 430 SUBEND 6 8 I O Path Attributes Character Code Pos 32 49 50 44 Outputting data to a string and then examining the string s contents is usually a more convenient method of examining output data streams than using a mass storage file A string may contain both printing and non printing control characters Printing string contents that contain control characters could interfere with examining the data stream The preceding subprogram may facilitate viewing this data without viewing such strings Example Outputs to string variables can also be used to generate the string representation of a number rather than using the VAL function or a user defined function subprogram The main advantage is that you can explicitly specify the number s image while still using only a single program line The following program compares the string generated by the VALS function to that generated by outputting the number to a string variable 100 X 12345678 110 120 PRINT VAL X 130 t 140 OUTPUT Val USING 3D E X 150 PRINT Val 160 170 END 1 2345678E 7 Printed results 123 E 05 Entering Data From String Variables Data are entered from string variables in much the same manner as output to the variable All ENTER statements that use string variables as the data source interpret the data according to the FORMAT ON attribute Data is read from the variable beginning at the first string position if su
36. aracters The I O Process I O Statements and Parameters Specifying a Resource Data Handshake Directing Data Flow Specifying a Resource String Variable Names Formatted String I O Device Selectors Select Codes of Built in Interfaces HP IB Device Selectors VO Paths es I O Path Names ReAssigning I O Path Kanes Closing I O Path Names I O Path Names in Subprograms 1 1 1 1 1 2 1 2 1 2 1 2 1 2 1 2 2 1 2 2 2 2 2 2 2 3 2 3 2 4 2 4 2 5 2 6 2 6 2 7 2 7 2 8 2 8 2 8 2 8 3 1 3 1 3 1 3 2 3 2 3 2 3 3 3 3 3 3 3 4 3 4 Contents 1 Assigning I O Path Names Locally Within Mob s Passing I O Names as Parameters Declaring I O Path Names in Common Benefits of Using I O Path Names Execution Speed coi Redirecting Data Access to Mass Storage Files Attribute Control 4 Outputting Data Introduction Free Field Outputs Examples i The Free Field Canvandon 4 Standard Numeric Format Standard String Format Item Separators and Terminators Changing the EOL Sequence Using END in Freefield OUTPUT Additional Definition xd END with HP IB Interfaces Examples Outputs that Use ages l The OUTPUT USING Statedent Images Example of Canes an es Image Definitions During Outputs Numeric Images Numeric Examples String Images String Examples Binary Images Binary Examples Special Character Images Special Character Examples Termination Images Termination Examples Additional Image Featu
37. are suppressed OUTPUT 1 Itemi Item2 i pet t if tle fm 2 Neither of the item teminators nor the EOL sequence are output If the item is an array the separator following the array name determines what is output after each array element Individual elements are output in row major order 110 DIM Array 1 2 1 3 120 FOR Row i TO 2 130 FOR Column i TO 3 140 Array Row Column Row 10 Column 150 NEXT Column 160 NEXT Row 170 180 OUTPUT CRT Array No trailing separator 190 200 OUTPUT CRT Array Trailing comma 210 220 OUTPUT CRT Array Trailing semi colon 230 4 240 OUTPUT CRT Done 250 END Outputting Data 4 3 Resultant Output Item separators cause similar action for string arrays 110 DIM Array 1 2 1 3 2 120 FOR Row 1 TO 2 130 FOR Column 1 TO 3 140 Array Row Column VAL Row 10 Column 150 NEXT Column 160 NEXT Row 170 180 OUTPUT CRT Array No trailing separator 190 200 OUTPUT CRT Array Trailing comma 210 y 220 OUTPUT CRT Array Trailing semi colon 230 240 OUTPUT CRT Done 250 END Resultant Output Eje 2 fomfer s fowler 2 fer ur 2 enn 2 9 ette sequence jejej a fonfer stefe 2 jenen 2 2 enn 2 5 esa sequence pinar ap er EOL sequence Changing the EOL Sequence t n end of line EOL sequence is normally sent following the last item sent with OUTPUT The default EOL sequence consists
38. ared in a variable common with COM statements and already be assigned within a context that has access to that common block The following paragraphs and examples further describe using I O path names in subprograms Assigning I O Path Names Locally Within Subprograms Any I O path name can be used in a subprogram if it has first been assigned to an I O path within the subprogram A typical example is shown below 10 CALL Subprogram x 20 END 30 40 SUB Subprogram x 50 ASSIGN Log device TO 1 CRT 60 OUTPUT Log device Subprogram 70 SUBEND 3 4 Directing Data Flow When the subprogram is exited all I O path names assigned locally within the subprogram are automatically closed If the program or subprogram that called the exited subprogram attempts to use the I O path name an error results An example of this closing local I O path names upon return from a subprogram is shown below 10 CALL Subprogram_x 11 OUTPUT 6Log device Main inserted line 20 END 30 40 SUB Subprogram x 50 ASSIGN 6Log device TO i CRT 60 OUTPUT Log device Subprogram TO SUBEND When the above program is run error 177 Undefined I O path name occurs in line 11 Each context has its own set of local variables These variables are not automatically accessible to any other context Consequently if the same I O path name is assigned to I O paths in separate contexts the assignment local to the context is used while in that contex
39. bsequent ENTER statements read characters from the variable the read also begins at the first position If more data are to be entered from the string than are contained in the string an error is reported however all data entered into the destination variable s before the end of the string was encountered remain in the variable s after the error occurs I O Path Attributes 6 9 When entering data from a string variable the computer keeps track of the number of characters taken from the variable and compares it to the string length Thus statement termination conditions are not required the ENTER statement automatically terminates when the last character is read from the variable However item terminators are still required f the items are to be separated and the lengths of the items are not known If the length of each item is known an image can be used to separate the items Example The following program shows an example of the need for either item terminators or length of each item The first item was not properly terminated and caused the second item to not be recognized 100 OUTPUT String ABC123 OUTPUT w o CR LF 110 120 t Now enter the data 130 ON ERROR GOTO Try again 140 1 150 First try 160 ENTER String Str Num 170 OUTPUT i First try results 180 OUTPUT 1 Str Str Num Num 190 BEEP Report getting this far 200 STOP 210 220 Try again OUTPUT 1 Error ERRN on ist try 230 OUTPU
40. cally in ENTER images The number builder can also be used to enter numeric data Numeric Specifiers Image Specifier Meaning D Specifies that one byte is to be entered and interpreted as a numeric character If the characters is non numeric including leading spaces and item terminators it will still consume one digit of the image item 2 Same action as D Keep in mind that A and can only appear to the left of the radix indicator decimal point or R in a numeric image item S M Same action as D in that one byte is to be entered and interpreted as a numeric character At least one digit specifier must follow either of these specifiers in an mage item Same action as D in that one byte is to be entered and interpreted as a numeric character At least one digit specifier must accompany this specifier in an image item Same action as D in that one byte is to be entered and interpreted as a numeric character however when R is used in a numeric image it directs the number builder to use the comma as a radix indicator and the period as a terminator to the numeric item At least one digit specifier must accompany this specifier in the image item E Equivalent to 4D if preceded by at least one digit specifier Z or D in the image item The following specifiers must also be preceded by at least one digit specifier ESZ Equivalent to 3D ESZZ Equivalent to 4D ESZZZ Equivalent to 5D Specifies
41. ce list Additional END Definition The END secondary keyword has been defined to produce additional action when included in an OUTPUT statement directed to HP IB interfaces END with HP IB interfaces With HP IB interfaces END has the additional function of sending the End or Identify signal EOT with the last character of either the last source item or the EOL sequence if sent As with freefield OUTPUT no EOI is sent if no gt data is sent from the last source item and the EOL sequence is suppressed Examples ASSIGN Device TO 701 OUTPUT Device USING K Data END OUTPUT Device USING K Data END t EOL Sequence Nan a EOI sent with last character of the EOL sequence OUTPUT Device USING K Data END Cose EOI sent with this character EOI is sent with the last character of the last source item when the EOL sequence is suppressed because the last source item contained data that was used in the output OUTPUT Device USING K Data END OUTPUT Device USING Data END Outputting Data 4 19 EEE The EOI was not sent in either case since no data were sent from the last source item and the EOL sequence was suppressed 4 20 Outputting Data Entering Data This chapter discusses the topic of entering data from devices You may already be familiar with the OUTPUT statement described in the previous chapter many of those concepts are applicable to the process of entering data Earli
42. d The EOL sequence is specified in one of the ASSIGN statements that describe the I O path Here i is an example that changes the EOL sequence to a single line feed character ASSIGN File TO file one EOL CHR 10 The characters following the secondary kevword EOL are the EOL characters Any character in the range CHR 0 through CHR 255 may be included in the string expression that defines the EOL characters however the length of the sequence is limited to eight characters or less If END is included in the EOL attribute an interface dependent END indication is sent with or after the last character of the EOL sequence However if no EOL sequence is sent the END indication is also suppressed The following statement shows an example of defining the EOL sequence to include an END indication ASSIGN Device TO 20 EOL CHR 13 amp CHR 10 END With the HP IB Interface the END indication is an End or Identify message EOI sent with the last EOL character The default EOL sequence is a CR and LF sent with no end indication This default can be restored by using the EOL OFF attribute I O Path Attributes 6 3 Restoring the Default Attributes If any attribute is specified the corresponding entry in the I O path name table is changed as above no other attributes are affected However if no attribute is assigned as below then all attributes are restored to their default state such as FORMAT ON for devices 340 AS
43. determining the characters output for numeric and string data are described in the following paragraphs Standard Numeric Format The default data representation for devices is to use ASCII characters to represent numbers The ASCII representation of each expression in the source list is generated during free field output operations Even though all REAL numbers have 15 and INTEGERs can have up to 5 significant decimal digits of accuracy not all of these digits are output with free field OUTPUT statements Instead the following rules of the free field convention are used when generating a number s ASCII representation Outputting Data 4 1 All numbers between 1E 5 and 1E 6 are rounded to 12 significant digits and output in floating point notation with no leading zeros If the number is positive a leading space is output for the sign if negative a leading is output For example 32767 32768 123456 789012 000123456789012 If the number is less than 1E 5 or greater than 1E 6 it is rounded to 12 significant digits and output in scientific notation No leading zeros are output and the sign character is a space for positive and for negative numbers For example 1 23456789012E 6 1 23456789012E 5 Standard String Format No leading or trailing spaces are output with the string s characters String characters No leading or trailing spaces item Separators and Terminators Data items are output one byte at a
44. e diagrams below internal Form p Data Computer Formatter Computer ASCH Data Memory Routine Resource Numeric Data Transformations with FORMAT ON With FORMAT OFF however no formatting is required The data items are merely copied from the source to the destination This type of I O operation requires less time since fewer steps are involved 1 O Path Attributes 6 1 Intemai Form Data Computer j Computer Memory Resource Numeric Data Transfer with FORMAT OFF The only requirement is that the resource also use the exact same data representations as the internal HP Instrument BASIC representation Here are how each type of data item is represented and sent with FORMAT OFF w INTEGER two byte 16 bit two s complement REAL eight byte 64 bit IEEE floating point standard String four byte 32 bit length header followed by ASCII characters An additional ASCII space character CHR 32 may be sent and received with strings in order to have an even number of bytes Here are the FORMAT OFF rules for OUTPUT and ENTER operations m No item terminator and no EOL sequence are sent by OUTPUT amp No item terminator and no statement termination conditions are required by ENTER s If either OUTPUT or ENTER uses an IMAGE such as with OUTPUT 701 USING 4D D then the FORMAT ON attribute is automatically used Assigning Default FORMAT Attributes As discussed in the Directing Data Flow cha
45. e entered but ignored not placed into a variable Specifies that all characters are to be entered but ignored not placed into a variable until a line feed is received EOI is also ignored until the line feed is received Examples of ignoring Characters Ignore first five and use second five characters ENTER Device USING 5X 5A Five_chars Ignore 6th through 9th characters ENTER Device USING 5A 4X 10A S_1 S_2 Ignore 1st item of unknown length ENTER Device USING K String2 Ignore two characters ENTER Device USING zz AA S 2 Binary Images These specifiers are used to enter one byte or word that will be interpreted as a number Binary Specifiers Image Specifier Meaning B Specifies that one byte is to be entered and interpreted as an integer in the range O through 255 W Specifies that one 16 bit word is to be entered and interpreted as a 16 bit two s complement INTEGER Since all HP Instrument BASIC interfaces are 8 bit two bytes are always entered the first byte entered is most significant If the source is a file or string variable all data are entered as bytes however one byte may still be entered and ignored when necessary to achieve alignment on a word boundary Like W except that pad bytes are never entered to achieve word alignment Entering Data 5 13 Examples of Binary Images Enter three bytes then look for LF or END indication ENTER Device USING B B B N1 N2 N3
46. e represented by a single byte 100 Number NUM A 110 PRINT Number Number 120 END prints Number 65 Representing Characters Data stored for humans is often alphanumeric type data Since less than 256 characters are commonly used for general communication a single data byte can be used to represent a character The most widely used character set is defined by the ASCII standard ASCII stands for American Standard Code for Information Interchange This standard defines the correspondence between characters and bit patterns of individual bytes Since this standard only defines 128 patterns bit 7 0 128 additional characters are defined by the computer bit 7 1 The entire set of the 256 characters on the computer is hereafter called the extended ASCII character set When the CHR function is used to interpret a byte of data its argument must be specified by its binary weighted value The single extended ASCII character returaed corresponds to the bit pattern of the function s argument interfacing Concepts 2 7 100 Number 65 Bit pattern is 01000001 110 PRINT Character is 120 PRINT CHR Number 130 END prints Character is The 1 0 Process When using statements that move data between memory and internal computer resources you do not usually need to be concerned with the details of the operations However you may have wondered how the computer moves the data This section describe
47. edges that it is ready 3 A data byte or word is placed on the data bus 4 The receiver acknowledges that it has gotten the data item and is now busy No further data may be sent until the receiver is ready 5 Repeat these steps if more data items are to be moved 2 8 interfacing Concepts 3 Directing Data Flow Data can be moved between computer memory and several resources These resources include amp Computer memory m Internal and external devices a Mass storage files This chapter describes in general terms how devices and string variables are specified in I O statements Each of these topics is covered in more detail in subsequent chapters This chapter also describes the use of I O pathnames in specifying devices for later use in I O statements Specifying a Resource Each resource must have a specifier that allows it to be accessed to the exclusion of all other computer resources String variables are specified by variable name while devices can be specified by either their device selector or a data type known as an I O path name This section describes how to specify these resources in OUTPUT and ENTER statements String Variable Names Data is moved to and from string variables by specifying the string variable s name in an OUTPUT or ENTER statement Examples of each are shown below 200 OUTPUT To_string Data_out suppresses CR LF 240 ENTER From_string To_string Data is always copied to the dest
48. ematical expressions Only eight levels of nesting are allowed END with OUTPUTs that Use Images Using the optional secondary keyword END in an OUTPUT statement that uses an image produces results that differ from those of using END in a freefield OUTPUT statement Instead of always suppressing the EOL sequence the END keyword only suppresses the EOL sequence when no data are output from the last source list expression Thus the ff image specifier generally controls the suppression of the otherwise automatic EOL sequence while the END keyword suppresses it only in less common usages Examples Device 12 OUTPUT Device USING K ABC END OUTPUT Device USING K ABC END OUTPUT Device USING K ABC END ajeje Et The EOL sequence is not suppressed Sequence OUTPUT Device USING L Literal X Q ps aaa A sequence sequence 4 18 Outputting Data In this case specifiers that require no source item expressions are used to generate characters for the output there are no source expressions The EOL sequence is output after all specifiers have been used to output their respective characters Compare this action to that shown in the next example OUTPUT Device USING L Literal X 0 END fo Jorperfi ipofe r of fr sequence The EOL sequence is suppressed because no source items were included in the statement all characters output were the result of specifiers that require no corresponding expression in the sour
49. er in this manual you were told that the data output from the sender had to match that expected by the receiver Because of the many ways that data is represented in external devices entering data can sometimes require more programming skill than outputting data In this chapter you will see what is involved in being the receiving device Both free field enters and enters that use images are described and several examples are given with each topic Free Field Enters Executing the free field form of the ENTER invokes conventions that are the converse of those used with the free field OUTPUT statement In other words data output using the free field form of the OUTPUT statement can be readily entered using the free field ENTER statement no explicit image specifiers are required The following statements exemplify this form of the ENTER statement For example ENTER Voltmeter Reading ENTER 724 Readings ENTER From_string Average Student_name ENTER From_file Data_code Str_element X Y Item Separators Destination items in ENTER statements can be separated by either a comma or a semicolon Unlike the OUTPUT statement it makes no difference which is used data will be entered into each destination item in a manner independent of the punctuation separating the variables in the list However no trailing punctuation is allowed The first two of the following statements are equivalent but an error is reported when the third
50. erstand each of the image specifiers used in the image list each will be fully described in subsequent sections of this chapter The main emphasis of this example is that you will see how an image list is used to govern the type and number of characters output OUTPUT CRT USING 6A SDDD DDD 3X K 123 45 The data stream output by the computer is as follows EDZEHEZEHBESUOHUOEEER 6A Si BD me Ue DADO 3X default EOL Sequence Step 1 The computer evaluates the first image in the list Generally each group of specifiers separated by commas is an image the commas tell the computer that the image is complete and that it can be processed In general each group of specifiers is processed before going on to the next group In this case 6 alphanumeric characters taken from the first item in the source list are to be output Step 2 The computer then evaluates the first item in the source list and begins outputting it one byte or word at a time After the 4th character the first expression has been exhausted In order to satisfy the corresponding specifier two spaces alphanumeric fill characters are output Step 3 The computer evaluates the next image note that this image consists of several different image specifiers The S specifier requires that a sign character be Outputting Data 4 7 Step 4 Step 5 Step 6 output for the number the D specifiers require digits of a numbe
51. ew assignment is then made just as if the first assignment never existed 100 ASSIGN Printer TO 1 Initial assignment 110 OUTPUT Printer Datai 120 130 ASSIGN Printer TO 701 t 2nd ASSIGN closes ist 140 OUTPUT Printer Data2 and makes a new assignment 150 PAUSE 160 END The result of running the program is that Datal is sent to the CRT and Data2 is sent to HP IB device 701 Closing 1 0 Path Names A second use of the ASSIGN statement is to ezplicitly close the name assigned to an I O path For example to close the path name Printer you would use the following statement ASSIGN Printer TO After executing this statement for a particular I O path name the name cannot be used in subsequent I O statements until it is reassigned I O Path Names in Subprograms When a subprogram either a SUB subprogram or a user defined function is called the context is changed to that of the called subprogram The statements in the subprogram only have access to the data of the new context Thus in order to use an I O path name in any statement within a subprogram one of the following conditions must be true m The I O path name must already be assigned within the context i e the same instance of the subprogram a The I O path name must be assigned in another context and passed to this context by reference i e specified in both the formal parameter and pass parameter lists w The I O path name must be decl
52. ext is not restored as in the preceding example since the I O path name is accessible to both contexts Directing Data Flow 3 5 In this example OLog device remains assigned to interface select code 1 thus Subprogram and Second Main are both directed to the CRT Declaring 1 0 Path Names in Common An I O path name can also be accessed by a subprogram if it has been declared in a COM statement labeled or unlabeled common to calling and called contexts as shown in the following example COM Log_device Insert COM statement ASSIGN Log_device to 701 4 OUTPUT Log_device First Main wo a 10 CALL Subprogram_x Parameters not necessary 11 OUTPUT Log_device Second Main 20 END 30 40 SUB Subprogram x Parameters not necessary 41 COM Log device Insert COM statement 50 ASSIGN Log device TO 1 CRT 60 OUTPUT Log_device Subprogram 70 SUBEND If an I O path name is common is modified in any way the assignment is changed for all subsequent contexts the original assignment is not restored upon exiting the subprogram In this example First Main is sent to the HP IB device 701 but Subprogram and Second Main are both directed to the CRT This is identical to the preceding action when the I O path name was passed by reference Benefits of Using I O Path Names Assigning names to I O paths provide improvements in performance and additional capabilities over using device selectors
53. external devices that are under computer control is an acronym that comes from Input and Qutput it refers to the process of copying data to or from computer memory involves moving data from computer memory to another resource During output the source of data is computer memory and the destination is any resource including memory is moving data from a resource to computer memory the source is any resource and the destination is a variable in computer memory Inputting data is also referred to as entering data in this manual for the sake of avoiding confusion with the INPUT statement refers to a common group of hardware lines that are used to transmit information between computer resources The computer communicates directly with the internal resources through the data and control buses interfacing Concepts 2 1 computer is an extension of these internal data and control buses The computer backplane communicates indirectly with the external devices through interfaces connected to the backplane hardware Why Do You Need an Interface The primary function of an interface is to provide a communication path for data and commands between the computer and its resources Interfaces act as intermediaries between resources by handling part of the bookkeeping work ensuring that this communication process flows smoothly The following paragraphs explain the need for interfaces First even though the computer bus i
54. iable names and I O path names in I O statements are described Chapter 4 Outputting Data This chapter presents methods of outputting data to devices All details of this process are discussed and several examples of free field output and output using images are given Since this chapter completely describes outputting data to devices you may only need to read the sections relevant to your application Chapter 5 Entering Data This chapter presents methods of entering data from devices All details of this process are discussed and several examples of free field enter and enter using images are given As with Chapter 4 you may only need to read sections of this chapter relevant to your application Chapter 6 I O Path Attributes This chapter presents several powerful capabilities of the I O path names provided by the BASIC language system Interfacing to devices is compared to interfacing to mass storage files and the benefits of using the same statements to access both types of resources are explained This chapter is also highly recommended to all readers Specific Interfaces Since each host instrument for HP Instrument BASIC implements the display keyboard and other interfaces in slightly different manners this manual does not cover the operation of interfaces For specific details on the operation of interfaces with HP Instrument BASIC consult the instrument specific manual for your host instrument 1 2 Manual Overvie
55. ices Built In Interface Device Permanent Select Code Built in HP IB interface Built in serial interface p The host instrument may have other built in interfaces See your instrument specific HP Instrument BASIC manual for information regarding these interfaces and their select codes HP IB Device Selectors Each device on the HP IB interface has a primary address by which it is uniquely identified each address must be unique so that only one device is accessed when one address is specified The device selector is then a combination of the interface select code and the device s address Some examples are shown below 3 2 Directing Data Flow HP IB Device Selector Examples Device Location Device Example I O Statement Selector interface select code 7 722 OUTPUT 722 Data ENTER primary address 22 722 Number interface select code 10 1001 OUTPUT 1001 Data ENTER primary address 01 1001 Number 1 0 Paths All data entered and output via an interface to files or devices is moved through an I O Path The I O paths to devices and mass storage files can be assigned special names called I O path names I O paths to strings cannot use I O path names The next section describes how to use 1 O path names along with the benefits of using them 1 O Path Names An I O path name is a data type that describes an I O resource With HP Instrument BASIC you can assign I O path names to either a device or a data file on a mass s
56. ination string or from the source string beginning at the first position of the variable subscripts cannot be used to specify any other beginning position within the variable Formatted String 1 0 The use of outputting to and entering from string variables is a very powerful method of buffering data to be output to other resources With OUTPUT and ENTER statements that use images the data sent to the string variables can be explicitly formatted before being sent to or while being received from the variable CN Directing Data Flow 3 1 Device Selectors Devices include an internal CRT keyboard external printers and instruments and all other physical entities that can be connected to the computer through an interface Each interface has a unique number by which it is identified known as its interface select code In order to send data to or receive data from a device merely specify the select code of its interface in an OUTPUT or ENTER statement Examples of using select codes to access devices are shown below OUTPUT i Data to CRT ENTER CRT Crt line HPib_device 722 OUTPUT 722 FiRi ENTER Hpib_device Reading The following pages explain select codes and device selectors Select Codes of Built In Interfaces The internal devices are accessed with the following permanently assigned interface select codes Note Some host instruments may not contain all of the following interfaces E Select Codes of Built in Dev
57. mber_1 receives the value 1 234567890123456 E 15 ENTER Device Real_number _2 Used only to build the exponent Consumed E SSE SSIS SI 5 Real_number_2 Terminator for both item and statement The result of entering the preceding data with the given ENTER statement is that Real_number_2 receives the value 1 234567890123456 E 17 4 Any exponent sent by the source must be preceded by at least one mantissa digit and an E or e character If no exponent digits follow the E or e no exponent is recognized but the number is built accordingly ENTER Device Real_number Consumed prm e fef fes ej rizje ejel jer Bou snis ja e pa Ignored Real_number Numeric Ignored Terminator item terminator The result of entering the preceding data with the given ENTER statement is that Real number receives a value of 8 85 E 12 The character C terminates entry into Real_number and the characters oul are entered but ignored in search of the required line feed statement terminator If the character C is to be entered but not ignored you must use an image Using images with the ENTER statement is described later in this chapter 5 4 Entering Data 5 If a number evaluates to a value outside the range corresponding to the type of the numeric variable an error is reported If no type has been declared explicitly for the numeric variable it is assumed to be REAL ENTER Device Real_number Consumed mm Pif
58. mma separator 4 2 Computer backplane 2 2 D Data Compatibility 2 2 Data Entering 5 1 Data Flow Directing 3 1 Data Handshake 2 8 Data Outputting 4 1 Data Re Directing 3 7 Data Representation Design Criteria 6 4 Data Representations 2 6 Data Representation Summary 6 7 Device Selectors 3 2 Digit specifier 4 9 Directing Data Flow 3 1 E Electrical and Mechanical Compatibility 2 2 END in Freefield OUTPUT 4 6 End of line EOL 4 2 End of line sequence 4 5 6 1 6 3 End or identify 5 7 5 14 END with HP IB Interfaces 4 6 4 19 END with OUTPUTs that Use Images 4 18 ENTER images 4 15 Entering Data 5 1 Entering String Data 5 5 ENTER statement 2 8 3 1 5 1 5 8 Enters that Use Images 5 8 ENTER USING statement 5 9 EOI Re Definition 5 14 Execution Speed 3 6 Explicitly close 3 4 Exponent specifier 4 9 F Files ASCII 6 6 Files BDAT 6 5 Files I O Paths to 6 5 FORMAT attributes 6 1 FORMAT Attributes Assigning Default 6 2 FORMAT OFF statement 3 7 6 1 FORMAT ON statement 3 7 6 1 FORMAT statement 6 1 Free Field Enters 5 1 Free Field ENTER Statements 5 7 Free field output 4 1 Freefield OUTPUT END in 4 6 H Handshake Data 2 8 HP IB Device Selectors 3 2 HP IB interface 2 4 j Image Definitions During Outputs 4 9 Image output 4 1 Image OUTPUT 4 1 Image Repeat Factors 4 16 Image Re Use 4 17 5 16 Images 4 7 5 9 Index 1 images binary
59. nce or two consecutive bytes of data are to be entered and interpreted as a two s complement integer 5 8 Entering Data The ENTER USING Statement The means by which you can specify how the computer will interpret the incoming data is to reference an image in the ENTER statement The four general ways to reference the image in ENTER statements are as follows 100 ENTER Device_x USING 6A DDD DD String var Num var 100 Image str 6A DDD DD 110 ENTER Device x USING Image str String var Num var 100 ENTER Device USING Image stmt String var Num var 110 Image stmt IMAGE 6A DDD DD 100 ENTER Device USING 110 String_var Num_var 110 IMAGE 64 DDD DD images Images are used to specify how data entered from the source is to be interpreted and placed into variables each image consists of one or more groups of individual image specifiers that determine how the computer will interpret the incoming data bytes or words Thus image lists can be thought of as a description of either a the format of the expected data or the procedure that the ENTER statement will use to enter and interpret the incoming data bytes The examples given here treat the image list as a procedure All of the image specifiers used in image lists are valid for both enters and outputs However most of the specifiers have a slightly different meaning for each operation If you plan to use the same image for output and enter you must fully underst
60. ng data execute in approximately the same amount of time Access to Mass Storage Files The third advantage of using I O path names is that device selectors cannot be used to direct data to or from mass storage files Therefore I O path names are the only access to files If the data is ever to be directed to a file you must use I O path names Attribute Control I O paths have certain attributes that control how the system handles data sent through the I O path For example the FORMAT attribute possessed by an I O path determines which data representation will be used by the path during communications If the path possesses the attribute of FORMAT ON the ASCI data representation will be used This is the default attribute automatically assigned by the computer when I O path names are assigned to device selectors If the I O path possesses the attribute of FORMAT OFF the internal data representation is used this is the default format for BDAT files Further details of these and additional attributes are discussed in the I O Path Attributes chapter The final factor that favors using I O path names is that you can control which attribute s are to be assigned to the I O path Attributes can be attached to an I O path name when it is assigned to a device via the ASSIGN statement and can specify data representation ASCII or internal as well as the end of line sequence for all data using the path Details of these attributes are
61. ng the L image specifier See Outputs that Use Images for further details Using END in Freefield OUTPUT The secondary keyword END may be optionally specified following the last source item expression in a freefield OUTPUT statement The result is to suppress the End of Line EOL sequence that would otherwise be output after the last byte of the last source item If a comma is used to separate the last item from the END keyword the corresponding item terminator will be output as before carriage return and line feed for string items and comma for numeric items The END keyword has additional significance when the destination is a mass storage file See the Data Storage and Retrieval chapter of HP Instrument BASIC Programming Techniques for further details Additional Definition HP Instrument BASIC defines additional action when END is specified in a freefield OUTPUT statement directed to the HP IB interface END with HP IB Interfaces With HP IB interfaces END has the additional function of sending the End or Identify signal EOD with the last data byte of the last source item however if no data is sent from the last source item EOI ts not sent Examples ASSIGN Device TO 701 OUTPUT Device 10 END BREE Van FO sent with the last character numeric item terminator Outputting Data 4 5 OUTPUT Device AB END AG p EOL sent with the last character of the item OUTPUT GDevice END OU
62. path TO x 360 370 Use FORMAT OFF during enter default 380 ASSIGN Io path TO B file 390 l Continued JO Path Attributes 6 5 400 Enter and print data and of characters 410 ENTER Data 420 PRINT LEN Data characters entered 430 PRINT 440 PRINT Data 450 ASSIGN Io_path TO Close 1 0 path 460 470 END ASCII Files ASCII files are designed for interchangeability with other HP computer systems This interchangeability imposes the restriction that the data must be represented with ASCII characters Each data item sent to these files is a special case of FORMAT ON representation each item is preceded by a two byte length header analogous to the internal form of string data In order to maintain this compatibility there are two additional restrictions placed on ASCII files m The FORMAT OFF attribute cannot be assigned to an ASCII file m You cannot use OUTPUT USING or ENTER USING with an ASCII file The following program shows the I O path name Io_path being assigned to the ASCII file named ASC_FILE Notice that the file name is in all uppercase letters this is also a compatibility requirement when using this file with some other systems The program creates an ASCII file and then outputs program lines to the file The program then gets and runs this newly created program If you type in and run this program be sure to save it on disc because running the program will load the program it create
63. patibility simply means that the connector plugs must fit together properly The interfaces connect with the computer buses The peripheral end of the interfaces have connectors that match those on peripherals Data Compatibility Just as two people must speak a common language the computer and peripheral must agree upon the form and meaning of data before communicating it As a programmer one of the most difficult requirements to fulfill before exchanging data is that the format and meaning of the data being sent is identical to that anticipated by the receiving device Even though some interfaces format data most do not most interfaces merely move data to or from computer memory The computer must make the necessary changes if any so that the receiving device gets meaningful information 2 2 Interfacing Concepts Timing Compatibility Since all devices do not have standard data transfer rates nor do they always agree as to when the transfer will take place a consensus between sending and receiving device must be made If the sender and receiver can agree on both the transfer rate and beginning point in time the process can be made readily If the data transfer is not begun at an agreed upon point in time and at a known rate the transfer must proceed one data item at a time with acknowledgement from the receiving device that it has the data and that the sender can transfer the next data item this process is known as a handshake
64. ple devices interfacing Concepts 2 5 Data Representations As long as data is only being used internally it really makes little difference how it is represented the computer always understands its own representations However when data is to be moved to or from an external resource the data representation is of paramount importance Bits and Bytes Computer memory is no more than a large collection of individual bits binary digits each _of which can take on one of two logic levels high or low Depending on how the computer interprets these bits they may mean on or not on off true or not true false one or zero busy or not busy or any other bi state condition These logic levels are actually voltage levels of hardware locations within the computer The following diagram shows the voltage of a point versus time and relates the voltage levels to logic levels Voltage of a Point 5v Logic High Logic Ground Logic Low Ov t t t Time 1 2 3 Voltage and Positive True Logic In some cases you want to determine the state of an individual bit of a variable in computer memory for instance The logical binary functions BIT BINCMP BINIOR BINEOR BINAND ROTATE and SHIFT provide access to the individual bits of data In most cases these individual bits are not very useful by themselves so the computer groups them into multiple bit entities for the purpose of representing more complex data Thus all data in com
65. pter names are assigned to I O paths between the computer and devices with the ASSIGN statement Here is a typical example ASSIGN Any_name TO Device selector This assignment fills a table in memory with information that describes the I O path This information includes the device selector the path s FORMAT attribute and other descriptive information When the I O path name is specified in a subsequent I O statement such as OUTPUT or ENTER this information is used by the system in completing the I O operation Different default FORMAT attributes are given to devices and files Devices since most devices use an ASCII data representation the default attribute assigned to devices is FORMAT ON This is also the default for ASCII files BDAT and HP UX or DOS files the default for BDAT and HPUX or DOS files is FORMAT OFF This is because the FORMAT OFF representation requires no translation time for numeric data this is possible because humans never see the data patterns written to the file and therefore the items do not have to be in ASCII or humanly readable form One of the most powerful features of this BASIC system is that you can change the attributes of I O paths programmatically 6 2 1 0 Path Attributes Specifying 1 0 Path Attributes There are two ways of specifying attributes for an I O path Specify the desired attribute s when the I O path name is initially assigned For example 100 ASSIGN De
66. puter memory are somehow represented with binary numbers The computer s hardware accesses groups of sixteen bits at one time through the internal data bus this size group is known as a word With this size of bit group 65 536 65 536 2 different bit patterns can be produced The computer can also use groups of eight bits at a time this size group is known as a byte With this smaller size of bit group 256 256 23 different patterns can be produced How the computer and its resources interpret these combinations of ones and zeros is very important and gives the computer all of its utility Representing Numbers The following binary weighting scheme is often used to represent numbers with a single data byte Only the non negative integers 0 through 255 can be represented with this particular scheme Most Significant Bit Least Significant Bit i Notice that the value of a 1 in each bit position is equal to the power of two of that position For example a 1 in the Oth bit position has a value of 1 1 2 a 1 in the Ist position has a value of 2 2 2 and so forth The number that the byte represents is then the total of all the individual bit s values 0x 29 0 1x2 2 1x2724 Number represented 0x2 1 x 24 16 2 4 16 128 150 0x2520 0x29 0 1 x 27 128 The preceding representation is used by the NUM function when it interprets a byte of data The next section explains why the character A can b
67. r and the specifies where the decimal point will be placed Thus the number of digits following the decimal point have been specified All of these specifiers describe the format of the next item in the source list The next data item in the source list is evaluated The resultant number is output one digit at a time according to its image specifiers trailing zero has been added to the number to satisfy the DDD specifiers following the decimal point The next image in the list 3X is evaluated This specifier does not require data so the source list needs no corresponding expression Three spaces are output by this image Since the entire image list and source list have been exhausted the computer then outputs the current or default if none has been specified end of line sequence of characters here we assume that a carriage return and line feed are the current EOL sequence The execution of the statement is now complete As you can see the data specified in the source list must match those specified in the output image in type and in number of items Image Definitions During Outputs This section describes the definitions of each of the image specifiers when referenced by OUTPUT statements The specifiers have been categorized by data type It is suggested that you scan through the description of each specifier and then look over the examples You are also highly encouraged to experiment with the
68. red the ENTER statement is automatically terminated as soon as the last image item is satisfied Also specifies that a statement termination condition is not required In addition EOI is redefined to be an immediate statement terminator allowing early termination of the ENTER before all image items have been satisfied However the statement can only be terminated on a legal item boundary The legal boundaries for different specifiers are as follows Specifier Legal Boundary K K With any character since this specifies a variable width field of characters S M D E Z A Only with the last character that satisfies the image e g with X literal B W the 5th character of a 5A image If EOI is received with any other character it is ignored Only with the last line feed character that satisfies the image e g with the 3rd line feed of a 3 image otherwise it is ignored i Specifies that an END indication is required to terminate the ENTER statement Line feeds are ignored as statement terminators however they will still terminate items unless a K or H image is used for strings Specifies that a line feed is required to terminate the statement EOI is ignored and other END indications such as EOF or end of data cause an error if encountered before the line feed Entering Data 5 15 Examples of Modifying Termination Conditions Enter a single byte ENTER Device USING B Byte Enter a single
69. res Repeat Factors Examples Image Re Use Nested Images END with OUTPUTs that Use fae Examples DE ta Additional END Definition l END with HP IB Interfaces Examples Contents 2 3 4 3 6 3 6 3 6 3 7 3 7 3 7 4 1 4 1 4 1 4 1 4 1 4 2 4 2 4 4 4 5 4 5 4 5 4 5 4 6 4 7 4 7 4 8 4 9 4 10 4 12 4 12 4 13 4 13 4 14 4 14 4 15 4 15 4 16 4 16 4 16 4 17 4 18 4 18 4 18 4 19 4 19 4 19 5 Entering Data Free Field Enters Item Separators Item Terminators 232 della de eom ess Entering Numeric Data with the Number Buildes Entering String Data Terminating Free Field ENTER Statements EOI Termination e wee o9 ae Enters that Use Images The ENTER USING Statement aor ea mapes e da He ae ha A EBS Example of an Enter Using an Image Image Definitions During Enter Numeric Images Examples of Numeric Images String Images ox ele Wee da cx Examples of String Images Ignoring Characters iu ii s Examples of Ignoring Characters Binary Images que e eov RN Examples of Binary Images Terminating Enters that Use Images Default Termination Conditions EOI Redefinition Statement Termination Modifiers Examples of Modifying Termination Conditions Additional Image Features PET Repeat Factors uni ee Image Reuse Gia lt XL ok E RUE er A Examples
70. rhead for numeric items that is there are no record headers for numeric items The transfer rates for each data type has also been increased Numeric output operations are always much faster because there is no time required for formatting Numeric enter operations are also faster because the system does not have to search for item and statement termination conditions In addition I O paths to BDAT and HP UX files can use either the ASCII FORMAT ON or the internal FORMAT OFF representation The following program shows a few of the features of BDAT files The program first outputs an internal form string with FORMAT ON and then enters the length header and string characters with FORMAT OFF 110 DIM Length 4 Data 256 Int_form 256 120 L 130 Create a BDAT file 1 record 256 bytes record 140 ON ERROR GOTO Aiready created 150 CREATE BDAT B file 1 160 Already created OFF ERROR 170 E 180 Use FORMAT ON during output 190 ASSIGN Io_path TO B_file FORMAT ON 200 l 210 Length CHR 0 amp CHR 0 Create length header 220 Length Length amp CHR 0 CHR 252 230 i 240 Generate 256 character string 250 Data 01234567 260 FOR Doubling 1 TO 5 270 Data Data amp Data 280 NEXT Doubling 290 Use only ist 252 characters 300 Data Data 1 252 310 t 320 Generate internal form and output 330 Int form Length amp Data 340 OUTPUT 6Io path Int form 350 ASSIGN QIo
71. rs Image Specifier Meaning i5 Specifies that one byte 8 bits of data is to be output The source expression is evaluated rounded to an integer and interpreted MOD 256 If it is less than 32 768 CHR 0 is output If is greater than 32 767 CHR 255 is output Ww Specifies that one word of data 16 bits are to be sent as a 16 bit two s complement integer The corresponding source expression is evaluated and rounded to an integer If it is less than 32 768 then 32 768 is sent if it is greater than 32 767 then 32 767 is sent If the destination is a BDAT or HPUX file or string variable the WORD attribute is ignored and all data are sent as bytes however pad byte s CHRS 0 will also be output whenever necessary to achieve alignment on a word boundary Since HP Instrument BASIC only supports 8 bit interfaces two bytes are always output with the most significant byte first This image specifier has been included primarily to maintain compatibility with HP Series 200 300 BASIC programs that include this specifier Y Like W except that no pad bytes are output to achieve alignment on a word boundary Binary Examples OUTPUT Device USING B B B 65 66 67 DOORS sequence OUTPUT Device USING B 13 OUTPUT Device USING W 256 65466 A EOL sequence Outputting Data 4 13 Special Character images These specifiers require no corresponding data in the source list They can be used to output
72. s destroying itself in the process 100 DIM Line 1 3 100 Array to store program 110 120 Create if not already on disc 130 ON ERROR GOTO Already exists 140 CREATE ASCII ASC_FILE 1 1 record 150 Already exists OFF ERROR 160 i 170 ASSIGN Io_path TO ASC FILE 180 STATUS Io_path 6 Pointer 190 PRINT Initially file pointer Pointer 200 PRINT 210 220 Line 1 100 PRINT New program 230 Line 2 110 BEEP 240 Line 3 120 END 250 t 260 OUTPUT Io_path Line 270 STATUS Io_path 6 Pointer 280 PRINT After OUTPUT file pointer Pointer 290 PRINT 300 310 GET ASC FILE Implicitly closes 1 0 path 320 330 END 6 6 1 0 Path Attributes Data Representation Summary The following table summarizes the control that programs have on the FORMAT attribute assigned to I O paths Program Control of the FORMAT Attribute Resource Attribute Used Attribute Be Changed HP UX or DOS files ASCU files FORMAT ON String variables FORMAT ON IFORMAT ON is always used whenever an OUTPUT USING or ENTER USING statement is used regardless of the FORMAT attribute assigned to the I O path 2The data representation used with ASCII files is a special case of the FORMAT ON representation Applications of Unified 1 0 This section describes two uses of the powerful unified I O scheme of the computer The first application contains further details and uses of I
73. s I O operations regarding how the computer outputs and enters data I O Statements and Parameters The I O process begins when an I O statement is encountered in a program The computer first determines the type of I O statement to be executed such as OUTPUT ENTER USING etc Once the type of statement is determined the computer evaluates the statement s parameters Specifying a Resource Each resource must have a unique specifier that allows it to be accessed to the exclusion of all other resources connected to the computer The methods of uniquely specifying resources output destinations and enter sources are device selectors string variable names and I O path names These specifiers are further described in the next chapter For instance before executing an OUTPUT statement the computer first evaluates the parameter that specifies the destination resource The source parameter of an ENTER statement is evaluated similarly OUTPUT Dest parameter Source item ENTER Sourc parameter Dest item Data Handshake Each byte or word of data is transferred with a procedure known as a data transfer handshake or simply handshake It is the means of moving one byte of data at a time when the two devices are not in agreement as to the rate of data transfer or as to what point in time the transfer will begin The steps of the handshake are as follows 1 The sender signals to get the receiver s attention 2 The receiver acknowl
74. s driven by electronic hardware that generates and receives electrical signals this hardware was not designed to be connected directly to external devices The internal hardware has been designed men specific electrical logic levels and drive capability in mind Second you cannot be assured that the connectors of the computer and peripheral are compatible In fact there is a good probability that the connectors may not even mate properly let alone that there is a one to one correspondence between each signal wire s function Third assuming that the connectors and signals are compatible you have no guarantee that the data sent will be interpreted properly by the receiving device Some peripherals expect single bit serial data while others expect data to be in 8 bit parallel form Fourth there is no reason to believe that the computer and peripheral will be in agreement as to when the data transfer will occur and when the transfer does begin the transfer rates will probably not match As you can see interfaces have a great responsibility to oversee the communication between computer and its resources Electrical and Mechanical Compatibility Electrical compatibility must be ensured before any thought of connecting two devices occurs Often the two devices have input and output signals that do not match if so the interface serves to match the electrical levels of these signals before the physical connections are made Mechanical com
75. statement is executed For example ENTER From_a_device N1 N2 N3 ENTER From_a_device N1 N2 N3 Entering Data 5 1 item Terminators Unless the receiver knows exactly how many characters are to be sent each data item output by the sender must be terminated by special character s When entering ASCII data with the free field form of the ENTER statement the computer does not know how many characters will be output by the sender Item terminators must signal the end of each item so that the computer enters data into the proper destination variable The terminator of the last item may also terminate the ENTER statement in some cases The actual character s that terminate entry into each type of variable are described in the next sections In addition to the termination characters each item can be terminated only with selected interfaces by a device dependent END indication For instance some interfaces use a signal known as EOI End or Identify The EOI signal is only available with the HP IB and keyboard interfaces EOI termination is further described in the next sections Entering Numeric Data with the Number Builder When the free field form of the ENTER statement is used numbers are entered by a routine known as the number builder This firmware routine evaluates the incoming ASCII numeric characters and then builds the appropriate internal representation number This number builder routine recognizes whether da
76. t Upon return to the calling context any I O path names accessible to this context remain assigned as before the context was changed 1 ASSIGN Log device to 701 Inserted line 2 OUTPUT Log_device First Main Inserted line 10 CALL Subprogram_x 11 OUTPUT 6Log device Second Main Changed line 20 END 30 40 SUB Subprogram x 50 ASSIGN Log device TO 1 CRT 60 OUTPUT Log_device Subprogran 76 SUBEND The results of the above program are that the outputs First Main and Second Main are directed to device 701 while the output Subprogram is directed to the CRT Notice that the original assignment of GLog device made to interface select code 1 was local to the subprogram Passing 1 0 Names as Parameters I O path names can be used in subprograms if they are assigned and have been passed to the called subprogram by reference they cannot be passed by value The I O path names s to be used must appear in both the pass parameter and formal parameter lists 1 ASSIGN 6Log device to 701 2 OUTPUT Log_device First Main 10 CALL Subprogram x Log device Add pass parameter 11 OUTPUT Log_device Second Main 20 END 30 40 SUB Subprogram_ x Log Add formal parameter 50 ASSIGN Log TO 1 CRT 60 OUTPUT Log Subprogram TO SUBEND Upon returning to the calling routine any changes made to the assignment of the I O path name passed by reference are maintained the assignment local to the calling cont
77. ta being entered is to be placed into an INTEGER or REAL variable and then generates the appropriate internal representation The number builder is designed to be able to enter several formats of numeric data However the general format of numeric data must be as follows to be interpreted properly by HP Instrument BASIC Mantissa Mantissa E Exponent Exponent Terminator digit s digit s character or END indication Optional At least Optional Required one digit is required Numeric characters include decimal digits 0 through 9 and the characters E and e These last five characters must occur in meaningful positions in the data stream to be considered numeric characters if any of them occurs in a position in which it cannot be considered part of the number it will be treated as a non numeric character 5 2 Entering Data The following rules are used by the number builder to construct numbers from incoming streams of ASCII numeric characters 1 All leading non numerics are ignored all leading and embedded spaces are ignored 100 ASSIGN Device TO Device selector 110 ENTER Device Number Default is data type REAL 120 END Consumed Ignored Number Terminator for both item and statement The result of entering the preceding data with the given ENTER statement is that Number receives a value of 123 The line feed statement terminator is required since Number is
78. time beginning with the left most item in the source list and continuing until all of the source items have been output Items zn the list must be separated by either a comma or a semicolon However items in the data output may or may not be separated by item terminators depending on the use of item separators in the source lists The general sequence of items in the data output is as follows The end of line EOL sequence is discussed in the next section item item EOL terminator terminator sequence Using a comma separator after an item specifies that the item terminator corresponding to the type of item will be output after the last character of this item A carriage return CHR 13 and a line feed CHR 10 terminate string items OUTPUT Device Item 1234 PTT TTD EET Tami ve so co nmn er sequence 4 2 Qutputting Data A comma separator specifies that a comma CHR 44 terminates numeric items OUTPUT Device si 1234 Item BRRBEHDBSEBBOEN sequence If a separator follows the last item in the list the proper item terminator will be output instead of the EOL sequence OUTPUT Device Item OUTPUT Device 1234 e fm je EA Using a semicolon separator suppresses output of the otherwise automatic item s terminator OUTPUT 1 Itemi Item2 l OUTPUT 1 12 34 Dnnasngnags M EEE eei sequence sequence If a semicolon separator follows the last item in the list the EOL sequence and item terminators
79. torage device The following examples show how this is done Devices ASSIGN Device TO 722 Piles ASSIGN File TO MyFile Once assigned the I O path names can be used in place of the device selectors to specify the resource with which communication is to take place For example ASSIGN Display TO 1 Assigns the I O path name Display to the CRT OUTPUT Display Data Sends characters to the display ASSIGN Printer TO 701 Assigns Printer to HP IB device 701 OUTPUT Printer Data Sends characters to the printer ASSIGN Gpio TO 12 Assigns Gpio to the interface at select code 12 ENTER Gpio A_number Enters one numeric value from the interface Note HP Instrument BASIC does not support assigning an I O path name to i multiple devices RL nRAA A edd Since an I O path name is a data type a fixed amount of memory is allocated for the variable similar to the manner in which memory is allocated to other program variables integer real and string This I O path information is only accessible to the context in which it was allocated unless it is passed as a parameter or appears in the proper COM statements ReAssigning I O Path Names If an I O path name already assigned to a resource is to be reassigned to another resource the preceding form of the ASSIGN statement is also used The resultant action is that the the Directing Data Flow 3 3 I O path name to the device is implicitly closed A n
80. use of these concepts 4 8 Outputting Data Numeric Images These image specifiers are used to describe the format of numbers Sign Digit Radix and Exponent Specifiers Image Specifier Meaning S Specifies a for positive and a for negative numbers is to be output M Specifies a leading space for positive and a for negative numbers is to be output D Specifies one ASCII digit 0 through 9 is to to be output Leading spaces and trailing zeros are used as fill characters The sign character if any floats to the immediate left of the most significant digit If the number is negative and no S or M is used one digit specifier will be used for the sign Same as D except that leading zeros are output This specifier cannot appear to the right of a radix specifier decimal point or R Like D except that asterisks are output as leading fill characters instead of spaces This specifier cannot appear to the right of a radix specifier decimal point or R Specifies the position of a decimal point radix indicator American radix within a number There can be only one radix indicator per numeric image item Specifies the position of a comma radix indicator European radix within a number There can be only one radix indicator per numeric image item Specifies that the number is to be output using scientific notation The E must be preceded by at least one digit specifier D Z
81. vice TO Dev selector FORMAT ON or 100 ASSIGN Device TO Dev selector Default for devices is FORMAT ON Specify only the attribute s in a subsequent ASSIGN statement 250 ASSIGN Device FORMAT OFF Change only the attribute The result of executing this last statement is to modify the entry in the I O path name table that describes which FORMAT attribute is currently assigned to this I O path The implicit ASSIGN Device TO which is automatically performed when the TO portion is included is not performed Also the I O path name must currently be assigned in this context or an error is reported Changing the EOL Sequence Attribute In addition to the FORMAT attributes another attribute is available to direct HP Instrument BASIC system to redefine the end of ine sequence normally sent after the last data item in output operations An end of line EOL sequence is normally sent following the last item sent with free field OUTPUT statements and when the L specifier is used in an OUTPUT that uses an image The default EOL characters are carriage return and line feed CR LP sent with no device dependent END indication You can also define your own special EOL sequences that include sending special characters sending an END indication and delaying a specified amount of time after sending the last EOL character In order to define non default EOL sequences to be sent by the OUTPUT statement an I O path must be use
82. w Interfacing Concepts This chapter describes the functions and requirements of interfaces between the host instrument and its resources Concepts in this chapter are presented in an informal manner All levels of programmers can gain useful background information that will increase their understanding of the why and how of interfacing Terminology These terms are important to your understanding of the text of this manual The purpose of this section is to make sure that our terms have the same meanings computer hardware software firmware computer resource 1 0 output input bus is herein defined to be the processor its support hardware and the HP Instrument BASIC language system of the host instrument together these system elements manage all computer resources describes both the electrical connections and electronic devices that make up the circuits within the computer any piece of hardware is an actual physical device describes the user written BASIC language programs refers to the preprogrammed machine language programs that are invoked by BASIC language statements and commands As the term implies firmware is not usually modified by BASIC users The machine language routines of the operating system are firmware programs is herein used to describe all of the data handling elements of the system Computer resources include internal memory display keyboard and disc drive and any
83. word ENTER Device USING W Integer Enter an array allowing early termination by EOI ENTER Device USING K Array Enter characters into String until line feed received then continue entering characters it until END received ENTER Device USING K String Enter characters until line feed received ignore EOI if received ENTER Device USING K String Additional Image Features Several additional image features are available with this BASIC language Some of these features have already been shown in examples and all of them resemble the additional features of images used with OUTPUT statements Repeat Factors All of the following specifiers can be preceded by an integer that specifies how many times the specifier is to be used Repeatable Specifiers Non Repeatable Specifiers Z D A X 0 L S M R E K H B W Y 4 image Reuse If there are fewer images than items in the destination list the list will be reused beginning with the first item in the image list If there are more images than there are items the additional specifiers will be ignored Examples The B is reused ENTER Device USING B B1 B2 B3 The W is not used ENTER Device USING 2A 2A W A B 5 16 Entering Data Nested Images Parentheses can be used to nest images within the image list The hierarchy is the same as with mathematical operations evaluation is from inner to outer sets of parentheses
84. xactly Only the number of numeric specifiers in the image here six is all that is used to specify the data format When all six characters have been entered the number builder attempts to form a number After the number is built it is placed into the variable Degrees the representation of the resultant number depends on the numeric variable s type INTEGER or REAL The next image in the IMAGE statement is evaluated It requires that one character be entered for the purpose of filling the variable Units One byte is then entered into Units All images have been satisfied however the computer has not yet detected a statement terminating condition A line feed or a character accompanied by EOI must be received to terminate the ENTER statement Characters are then entered but ignored in search of one of these conditions The statement is terminated when the EOI is sent with the t For further explanation see Terminating Enters that Use Images The above example should help you to understand how images are used to determine the interpretation of incoming data The next section will help you to use each specifier to create your desired images image Definitions During Enter This section describes the individual image specifiers in detail The specifiers have been categorized into data and function type 5 10 Entering Data Numeric Images Sign digit radix and exponent specifiers are all used identi
85. xample given with rule 4 describing the number builder If a trailing non numeric character terminates the last item which is a numeric variable additional characters will be entered in search of either a line feed or a character accompanied by EOI Unless this terminating condition is found before 256 characters have been entered an error is reported EOI Termination A termination condition for the HP IB Interface is the EOI End or Identify signal When this message js sent it immediately terminates the entire ENTER statement regardless of whether or not all variables have been satisfied However if all variable items in the destination list have not been satisfied an error is reported For example ENTER Device String ISTE Te Te STSTE Te Te TF Te 4 T8 Te Te Te T Tes tay Sent with Sent with Sent with EO EOI EOt The result of entering the preceding data with the given ENTER statement is that String receives the characters ABCDEF The EOI signal being received with either the last character or with the terminator character properly terminates the ENTER statement If the character accompanied by EOI is a string character not a terminator it is entered into the variable as usual Entering Data 5 7 For example ENTER Device Number Used to build Number Consumed Consumed mn n A Pi f2tsfels or or Number Sent with Number Sent with Number Sent with EO EOI EOI The result of entering

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