Word Pro - HM PC-CARD
Contents
1. Data is written to and read from this port in bytes If programmed for output a write to this register will update the outputs A zero sets the output to TTL Low A one sets the output to TTL High NOTE TTL High is not necessarily 5V The current high low bit settings can be read back from the port by reading it If programmed for input a read will capture the current state of all eight input lines eight bits of the port Writing to an input port has no function 11 7 2 8 BASE 5 2nd DIO Port B READ WRITE ITA A ee B7 Bo BS B4 B3 B2 Bi BO The direction of this port is set by writing a control word to BASE 7 The port is one byte wide and can be set as eight in or eight out Data is written to and read from this port in bytes If programmed for output a write to this register will update the outputs A zero sets the output to TTL Low A one sets the output to TTL High NOTE TTL High is not actually 5V but something less The current high low bit settings can be read back from the port by reading it If programmed for input a read will capture the current state of all eight input lines 8 bits of the port Writing to an input port has no function 7 2 9 BASE 6 2nd DIO Port C READ WRITE 7 6 5 4 3 2 1 0 CH7 CH6 CH5 CH4 CL3 CL2 CLI CLO The direction of port C is set by writing a control word to BASE 7 The port is one byte wide but can be configured in two 4 bit ni2. IO hardware The complete InstaCal package is also included with the Universal Library If you have ordered the Universal Library use the Universal Library disk set to install InstaCal The installation will create all required files and unpack the various pieces of compressed software To install InstaCal refer to the Extended Software Installation Manual for complete instructions 3 HARDWARE INSTALLATION The PC CARD DIO48 is completely plug and play There are no switches or jumpers to set Configuration is controlled by your systems PCMCIA software Simply insert the PC CARD DIO48 into any available slot Refer to the orientation guide below for proper orientation of the card the typical system orients the card with the label up Figure 3 1shows a PCM card case looking into the connector which is inserted into the PCMCIA slot of your computer The key helps to insure that the board is inserted correctly Key Side A Top Side This side has the label Side B Bottom Side No label here PCMCIA CARD ORIENTATION View into PCMCIA connector The end which qoes into the PCMCIA slot Figure 3 1 Card Orientation If you are using an operating system with support for Plug and Play such as Windows 95 or 98 a dialog box will pop up upon insertion of the card indicating that new hardware has been detected If the information file for this board is not already loaded onto your PC you will be prompted for a disk containi
3. Independent Function Input Output M1 0 is mode 0 for group B Input Output M1 1 is mode for group B Strobed Input Output The Ports A B C High CH and C Low CL can be independently programmed for input or output The two groups of 82C55 ports group A and group B can be independently programmed in one of several modes The most commonly used mode is mode 0 input output mode The codes for programming the 82C53 in this mode are in Table 7 2 10 Table 7 2 82C55 Mode 0 Programming Modes D4 D3 D1 D0 HEX DEC A B CU CL 0 0 0 0 80 128 OUT OUT OUT OUT 0 0 0 1 81 129 OUT OUT OUT IN 0 0 1 0 82 130 OUT IN OUT OUT 0 0 1 1 83 131 OUT IN OUT IN 0 1 0 0 88 136 OUT OUT IN OUT 0 1 0 1 89 137 OUT OUT IN IN 0 1 1 0 8A 138 OUT IN IN OUT 0 1 1 1 8B 139 OUT IN IN IN 1 0 0 0 90 144 IN OUT OUT OUT 1 0 0 1 91 145 IN OUT OUT IN 1 0 1 0 92 146 IN IN OUT OUT 1 0 1 1 93 147 IN IN OUT IN 1 1 0 0 98 152 IN OUT IN OUT 1 1 0 1 99 153 IN OUT IN IN 1 1 1 0 9A 154 IN IN IN OUT 1 1 1 1 9B 155 IN IN IN IN D7 is always one D6 D5 and D2 are always zero 7 2 7 BASE 4 2nd DIO Port A READ WRITE 7b 6 5 4 3 2 1 0 A7 A6 A5 A4 A3 A2 Al AO The I O direction of this port is set by writing a control word to BASE 7 The port is one byte wide and can be set as eight in or eight out
4. The pull up resistor holds the output at REGISTER 5V if not driven low by the register The Amex CONDITIONER value of 2 2K ohms requires only 2 3 mA BOWN FIELD DEVICE of drive current E If the board is reset and enters high impedance input the line is pulled high Figure 9 1 Pull up Pull Down Resistors 15 At that point both the board AND the device being controlled will sense a high signal In output mode when a 1 is written to the output bit the register has enough power to override the pull up resistor s current and drive the line to O volts A pull down resistor accomplishes the opposite task in that the line is pulled low when the board is reset The register has enough power to drive the line high A resistor value of 2 2K is recommended Use other values only if you have determined the necessity for doing so 9 2 TTL TO SOLID STATE RELAYS Many applications require digital inputs to monitor AC and DC voltages High AC and DC voltages cannot be applied directly by the TTL digital lines Solid State Relays such as those available from Measurement Computing Corp allow control and monitoring of high AC and DC voltages and provide 400V isolation Solid State Relays SSRs are recommended for interfacing to high voltages The most convenient way to use solid state relays is to purchase a Solid State Relay Rack SSR Racks are available from Measurement Computing Corp 9 3 VOLTAGE DIVIDERS An alternative method of
5. 2 3 BASE 0 IstDIO PortA ooooooocooooomoomo o ooo 8 7 24 BASE 1 IstDIOPortB oo ooooocooocmcoomo E 8 7 2 5 BASE 2 IstDIOPortC ooooocoocmocronomomomooo 9 7 2 6 BASE 3 Ist 82C55 Configuration Register 9 7 2 7 BASE 4 2nd DIO Port A einen ai ei e ee eee 11 7 2 8 BASE 5 2nd DIO PortB 0 cee ee eee 12 7 2 9 BASE 6 2nd DIO PorttC o oocoocoocmocmocnocno eee 12 7 2 10 BASE 7 2nd 82C55 Configuration Register 12 8 SPECIFICATIONS uscar rr ea ale SEA EE A eA 14 9 ELECTRONICS AND INTERFACING 0 000000 0c eee 15 9 1 PULL UP PULL DOWN RESISTORS 2 000220 ee 15 9 2 TTL TO SOLID STATE RELAYS sorsia ie eiaa a eee 16 9 3 VOLTAGE DIVIDERS 0 r eiae i eee ene 16 9 4 LOW PASS FILTERS DE BOUNCE INPUTS This page is blank 1 INTRODUCTION The PC CARD DIO48 is a data acquisition and control board for IBM PC compatible computers having PC CARD PCMCIA type slots The primary functional elements of the board are a pair 82C55 digital I O chips The 82C55 chip uses TTL logic Each has 24 digital bi directional input or output channels Figure 1 1 82C55 AO 7 0 IGI BO 7 0 IGI C CO 7 0 DATA BUS a r l i PC CARD DIO48 82055 _ ADDRESS BUS Figure 1 1 PC CARD DIO48 Block Diagram 2 SOFTWARE INSTALLATION InstaCal is the installation calibration and test software supplied with your data acquisition
6. L High is not actually 5V but something less The current high low bit settings can be read back from the port by reading it If programmed for input a read will capture the current state of all eight input lines eight bits of the port Writing to an input port has no function 72 4 BASE 1 Ist DIO Port B READ WRITE E AA MET EA O A 8 B7 Bo B5 B4 B3 B2 Bi BO The direction of this port is set by writing a control word to BASE 3 The port is one byte wide and can be set as eight in or eight out Data is written to and read from this port in bytes If programmed for output a write to this register will update the outputs A zero sets the output to TTL Low A one sets the output to TTL High NOTE TTL High is not actually 5V but something less The current high low bit settings can be read back from the port by reading it If programmed for input a read will capture the current state of all eight input lines 8 bits of the port Writing to an input port has no function 72 5 BASE 2 Ist DIO Port C READ WRITE 7 6 5 4 3 2 1 0 CH7 CH6 CH5 CH4 CL3 CL2 CLI CLO The direction of this port is set by writing a control word to BASE 3 The port is one byte wide but can be configured in two 4 bit nibbles It can be set as eight in eight out or split to four in and four out Data is written to and read from this port in bytes even when split as four four The rules for writing and rea
7. PC CARD DIO48 User s Manual A AY MEASUREMENT COMPUTING Revision 5 August 2001 MEGA FIFO the CIO prefix to data acquisition board model numbers the PCM prefix to data acquisition board model numbers PCM DAS08 PCM D24C3 PCM DAC02 PCM COM422 PCM COM485 PCM DMM PCM DAS16D 12 PCM DAS16S 12 PCM DAS16D 16 PCM DAS16S 16 PCI DAS6402 16 Universal Library InstaCal Harsh Environment Warranty and Measurement Computing Corporation are registered trademarks of Measurement Computing Corporation IBM PC and PC AT are trademarks of International Business Machines Corp Windows is a trademark of Microsoft Corp All other trademarks are the property of their respective owners Information furnished by Measurement Computing Corp is believed to be accurate and reliable However no responsibility is assumed by Measurement Computing Corporation neither for its use nor for any infringements of patents or other rights of third parties which may result from its use No license is granted by implication or otherwise under any patent or copyrights of Measurement Computing Corporation All rights reserved No part of this publication may be reproduced stored in a retrieval system or transmitted in any form by any means electronic mechanical by photocopying recording or otherwise without the prior written permission of Measurement Computing Corporation Notice Measurement Computing Corporation does not authorize any Measurement Co
8. bbles It can be set as eight in eight out or split to four in and four out Data is written to and read from this port in bytes even when split as four four The rules for writing and reading data apply regardless of whether eight or four four operation is used If programmed for output a write to this register will update the outputs A zero sets the output to TTL Low A one sets the output to TTL High The current high low bit settings can be read back from the port by reading it If programmed for input a read will capture the current state of all eight input lines 8 bits of the port Writing to an input port has no function 7 2 10 BASE 7 2nd 82C55 Configuration Register WRITE 7 6 5 4 3 2 1 0 1 MS 0 M3 0 M2 D4 A D3 CU 0M1 D1 B DO CL Group A Group B The 82C55 can be programmed to operate in Input Output mode 0 Strobed Input Output mode 1 or Bi Directional Bus mode 2 12 To program the 82C55 for other modes the following control code byte must be assembled into an 8 bit byte MS Mode Set 1 mode set active M3 M2 Group A Function 0 0 Mode 0 Input Output 0 1 Mode 1 Strobed Input Output 1 X Mode 2 Bi Directional Bus A B CL CH Independent Function 1 1 1 1 Input 0 0 0 Output M1 0 is mode 0 for group B Input Output MI 1 is mode 1 for group B Strobed Input Output The Ports A B C High CH and C Low CL can be independent
9. ding data apply regardless of eight or four four operation If programmed for output a write to this register will update the outputs A zero sets the output to TTL Low A one sets the output to TTL High NOTE TTL High is not necessarily 5V The current high low bit settings can be read back from the port by reading it If programmed for input a read will capture the current state of all eight input lines 8 bits of the port Writing to an input port has no function 7 2 6 BASE 3 1st 82C55 Configuration Register WRITE 7 6 5 4 3 2 1 0 1 MS 0 M3 0 M2 D4 A D3 CU 0M1 D1 B DO CL Group A Group B The 82C55 can be programmed to operate in Input Output mode 0 Strobed Input Output mode 1 or Bi Directional Bus mode 2 Information on programming the 82C55 in mode 0 is included here To program an 82C55 for Mode 1 or 2 you will need the Applications Manual that is available at www measurementcomputing com 82c55 When the PC is powered up or RESET the 82C55 is reset This places all 48 lines in Input mode and no further programming is needed to use the 48 lines as TTL inputs To program the 82C55 for other modes the following control code byte must be assembled into an 8 bit byte MS Mode Set 1 mode set active M3 M2 0 0 0 1 1 X A B CL 1 1 1 0 0 O Group A Function Mode 0 Input Output Mode 1 Strobed Input Output Mode 2 Bi Directional Bus
10. eld requirements for industrial process measurements and control equipment IEC 801 4 Electrically fast transients for industrial process measurement and control equipment Carl Haapaoja Director of Quality Assurance Measurement Computing Corporation 16 Commerce Boulevard Middleboro Massachusetts 02346 508 946 5100 Fax 508 946 9500 E mail info measurementcomputing com WWW measurementcomputing com
11. high and turn the device on If you are using the PC CARD DIO48 to control a digital device and it is critical that it remain off outputs grounded on power up or reset attach 2 2K Ohm pull down resistors to each output line Remember if you have the 82C55 interfaced to an input chip when the computer is powered up you have an input connected to an input This is an undefined connection Unconnected inputs will float If you are using the board for inputs and have unconnected inputs ignore the data from those lines For example if you connect bit AO and not bit Al do not be surprised if Al stays low stays high or tracks AO It is unconnected and as such is unspecified The input buffer is not malfunctioning In the absence of a pull up pull down resistor any input which is unconnected is unspecified The nature of the input means it will typically float high However depending on the drive requirements of the device you are driving they may float up or down The way they float is dependent on the characteristics of the circuit and the electrical environment and may be unpredictable This is why it often appears that the board outputs have gone high after power up The result is that the controlled device gets turned on That is why you need pull up down resistors i Figure 9 1 shows digital outputs with a om PULL UP pull up resistor and a pull down resistor ia COND TIONER attached wary an FIELD DEVICE
12. l signal that is at 0 volts when off and 24 volts when on you cannot connect that directly to a digital input The voltage must be dropped to 5 volts max when on The attenuation is 24 5 or 4 8 Using the equation above if R2 is 1K R1 4 8 1 x 1000 3 8K Remember that a TTL input is on when the input voltage is greater than 2 5 volts NOTE The resistors R1 and R2 are going to dissipate power in the divider circuit according to the equation W P x R Current I Voltage Resistance Here is a simple rule For attenuation of lt 5 1 no resistor should be less than 10K For attenuation of gt 5 1 no resistor should be less than 1K 17 9 4 LOW PASS FILTERS DE BOUNCE INPUTS A low pass filter can be installed between a source and a board It prevents frequencies higher than the cutoff frequency from entering the board s inputs The cutoff frequency is that frequency above which no variation of voltage with respect to time may enter the circuit For example if a low pass filter had a cutoff frequency of 30 Hz interference associated with line voltage 60 Hz would be mostly filtered out but a signal of 25 Hz would pass with less attenuation Also a low pass filter is often used to remove contact bounce noise signals from a switch or a relay contacts In a digital circuit a low pass filter can be used to de bounce an input from a switch or external relay Unless switch relay contacts are mercury whetted they tend to b
13. ly programmed for input or output The two groups of ports group A and group B can be independently programmed in one of three modes The most commonly used mode is mode 0 input output mode NOTE Measurement Computing s Universal Library supports 82C55 Mode 0 only The codes for programming the 82C55 in mode 0 are in Table 7 2 13 8 SPECIFICATIONS Typical for 25 C unless otherwise specified POWER CONSUMPTION 5V normal operation DIGITAL I O Digital Type Configuration Number of channels Output High Output Low Input High Input Low Power up reset state ENVIRONMENTAL Operating temperature range Storage temperature range Humidity 37 mA typical 55 mA max 82C55 4 ports of 8 each plus 4 nibbles of 4 each programmable by port or nibble as input or output 48 I O 3 7 volts min 2 5 mA 0 4 volts max 2 5 mA 2 2 volts min 5 5 volts absolute max 0 8 volts max 0 5 volts absolute min Input mode high impedance 0 to 70 C 40 to 100 C 0 to 95 non condensing 14 9 ELECTRONICS AND INTERFACING This short simple introduction to the electronics most often needed by digital I O board users covers a few key concepts 9 1 PULL UP PULL DOWN RESISTORS NOTE ON 82C55 PLEASE READ The 82C55 when powered up or reset defaults all data lines to the input mode This presents a high impedance With some TTL input chips the 82C55 high impedance input can cause the input to float
14. measuring a signal which varies over a range greater than the input range of a digital input is to use a voltage divider When correctly designed it can drop the voltage of the input signal to a safe level the digital input can accept Ohm s law states Voltage Current x Resistance Kirkoff s law states The sum of the voltage drops around a circuit will be equal to the voltage drop for the entire circuit In a voltage divider the voltage across one resistor in a series circuit is proportional to the total resistance divided by the one resistor see formula in Figure 9 2 and below The object in a voltage divider is to choose two resistors having the proportions of the maximum voltage of the input signal to the maximum allowed input voltage 16 The formula for attenuation is Attenuation R1 R2 R2 For example if the signal varies between 0 and 20 2 10K 10K volts and you wish to measure that with an analog 10K input with a full scale range of 0 to 10 volts the attenuation A is 2 1 or just 2 R1 A 1 x R2 For a given attenuation pick a resistor and call it R2 the use this formula to calculate R1 SIGNAL HIGH A Vin R1 R2 Vout R2 R1 V1 BOARD SIGNAL HIGH INPUT VOLTS gt Vin R2 v2 Vout BOARD SIGNAL LOW T LOW INPUT gt SIMPLE VOLTAGE DIVIDER Figure 9 2 Voltage Divider Schematic Digital inputs often require the use of voltage dividers For example if you wish to measure a digita
15. mputing Corporation product for use in life support systems and or devices without the written approval of the President of Measurement Computing Corporation Life support devices systems are devices or systems which a are intended for surgical implantation into the body or b support or sustain life and whose failure to perform can be reasonably expected to result in injury Measurement Computing Corp products are not designed with the components required and are not subject to the testing required to ensure a level of reliability suitable for the treatment and diagnosis of people C Copyright 2001 Measurement Computing Corporation HM PC CARD DIO48 lwp TABLE OF CONTENTS TINTRODUCTION Jaia Sted a a A Ba ata 1 2 SOFTWARE INSTALLATION 0 0 ee eee 1 3 HARDWARE INSTALLATION 0 0 00 ce cee eee eee 2 4 INTERFACING o ii ie Gee iind r ale oe hee a ake 3 4 1 PC CARD DIO48 CONNECTOR we es 3 AO CABLING Sriti a Stas Le A A Glas Pee cay a seis 4 5 PROGRAMMING amp APPLICATIONS 0 0 0 0 000 ce eee 6 5 1 PROGRAMMING LANGUAGES 1 ee ee ee 6 5 2 PACKAGED APPLICATIONS PROGRAMS we ee ee ee 6 6 CALIBRATION amp SERVICES 00 ee eee 6 71 0 ADDRESS MAP amp REGISTER FUNCTIONS 7 7 1 CONTROL REGISTERS s 0 0 eee ee eee 7 7 2 PORT ADDRESSES 8 FUNCTIONS 2 0 2 0 00 0 cee eee eens 7 1 2 1 CORR Register indio da li hes Bsns alas ae Oh n a a 8 7 22 CESR Registe ata da tee eet ew a 8 7
16. nal board or other signal conditioning interface board The first is a CPCC 50F 39 cable It is 39 inches 990mm long and is compatible with all standard 50 pin screw terminal products such as the CIO MINISO and SCB 50 Refer the connector diagram above Figure 4 1 for the functions of the signals at the screw terminals As an alternative the CPCC 50M 4 is a four inch long adapter cable It is required when a CSOFF series cable is to be used See Figure 4 2 for a map of the two methods of cabling from the PC CARD DIO48 to one of a variety of screw terminal or signal conditioning boards Figure 4 3 is a cable map of the ways that two SSR RACK24 or CIO ERB24 relay racks can be cabled to the PC CARD DIO48 a TERMINALS RELAYS LL A CIO MINI50 SSR RACK24 PC CARD DIO48 z CIO SPADE 50 CIO ERB48 FOSA Y CIO TERM100 CIO ERB24 C50FF SCB 50 CIO SERB48 CPCC 50M 4 CIO SERB24 OR __ TERMINALS RELAYS __ _ YR CIO MINI50 SSR RACK24 PC CARD DIO48 y CIO SPADE 50 CIO ERB48 T e CIO TERM100 CIO ERB24 SCB 50 CIO SERB48 CPCC 50F 39 CIO SERB24 Figure 4 2 Cable Maps CPCC 50F 39 PC CARD DIO48 EA f C50FF CPCC 50M 4 CIO ERB24 or SSR RACK24 CIO ERB24 or SSR RACK24 Figure 4 3 Cable Map to CIO ERB24 or SSR RACK24 5 PROGRAMMING amp APPLICATIONS 5 1 PROGRAMMING LANGUAGES Universal Library provides complete access to the PC CARD DIO48 functions fr
17. ng it The InstaCal software that was supplied with your board as well as the optional Universal Library software contains this file Just insert the disk or CD and click OK In order to easily test your installation it is recommended that you install InstaCal the installation calibration and test utility that was supplied with your board Refer to the Extended Software Installation Manual for information on the initial setup loading and installation of InstaCal and optional Universal Library software 4 INTERFACING The PC CARD DIO48 has 48 digital input output channels The 48 I O channels are processed by two 82C55 chips each chip handling three ports A B and C 24 channels total per 82C55 4 1 PC CARD DIO48 CONNECTOR Figure 4 1 is a PC CARD DIO48 case looking into the connector The key helps to insure that the cable is inserted in the correct orientation Key LAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAJ PORT NO PORT NO O CO N olaj AO N ery o _ mi N A al o N foe o N o N mk N N N oo N A oo PO PO PO PO PY PO PS NINININI NI PO PY PO PO PO NINININI N Po N N al Figure 4 1 I O Connector Pin out amp Orientation 3 4 2 CABLING Measurement Computing offers two cables for connecting the PC CARD DIO48 to a screw type termi
18. om a range of programming Windows languages If you are planning to write programs or would like to run the example programs for Visual Basic or any other language please turn now to the Universal Library manual 5 2 PACKAGED APPLICATIONS PROGRAMS Many packaged application programs such as SoftWIRE have drivers for the PC CARD DIO48 If the package you own does not appear to have drivers please call us with the package name and the revision number from the install disks We will research the package for you and advise you on how to obtain the correct drivers 6 CALIBRATION amp SERVICES There is no calibration required The case cannot be opened and there are no parts inside which you can service There are no socketted components Opening the PC CARD DIO48 case will void your warranty If you PC CARD DIO48 requires service please contact the factory for an RMA and return it 7 YO ADDRESS MAP amp REGISTER FUNCTIONS A base address register controls the beginning or Base address of the I O addresses occupied by the registers of the PC CARD DIO48 Nine addresses are used The base address is assigned by PCMCIA software read by InstaCal and stored in the CB CFG file installed in your computer Please read about installing and using InstaCal 7 1 CONTROL REGISTERS After installation and a base address has been established the PC CARD DIO48 can be controlled by reading and writing to the registers While it is possible
19. ounce briefly on closure generating a pulsating noise signal This can easily lead to erroneous counts unless filtered out A simple low pass filter can be constructed from one resistor R and one capacitor C The cutoff frequency is determined according to the formula gt gt Signal 7 i A D Board High R High Input TG Signal Volts Signal A D Board Low y ee Input LOW PASS FILTER F 1 2 Pi R C Figure 9 3 Low Pass filter Schematic Fc 1 Where n 3 14 2TRC R ohms C farads R 1 Fc cutoff frequency in cycles second 2n C Fe 18 EC Declaration of Conformity We Measurement Computing Corporation declare under sole responsibility that the product PC CARD DIO48 PCMCIA Digital I O Board Part Number Description to which this declaration relates meets the essential requirements is in conformity with and CE marking has been applied according to the relevant EC Directives listed below using the relevant section of the following EC standards and other normative documents EU EMC Directive 89 336 EEC Essential requirements relating to electromagnetic compatibility EU 55022 Class B Limits and methods of measurements of radio interference characteristics of information technology equipment EN 50082 1 EC generic immunity requirements IEC 801 2 Electrostatic discharge requirements for industrial process measurement and control equipment IEC 801 3 Radiated electromagnetic fi
20. to write your own control routines many have been written and are available in Universal Library for Windows programming languages NOTE ON REGISTER PROGRAMMING SUPPORT Only limited support for assembly language or direct register programming is available Register level programming should only be attempted by experienced programmers We support the use of the PC CARD DIO48 through high level languages using Universal Library and the example programs provided 7 2 PORT ADDRESSES amp FUNCTIONS Table 7 1 lists the card registers and their function All registers perform 8 bit byte operations A Port C can be divided into two 4 bit ports CU upper and CL lower Table 7 1 Card Register Functions 7 2 1 CORR Register 7 6 5 4 3 2 1 0 X X X X X X X X There are no functions supported in the COR 7 2 2 CCSR Register 7 6 5 4 3 2 1 0 X X X X X X X X There are no functions supported in the CCSR 7 2 3 BASE 0 Ist DIO Port A READ WRITE 7b 6 5 4 3 2 1 0 A7 A6 A5 A4 A3 A2 Al AO The direction of this port is set by writing a control word to BASE 3 The port is one byte wide and can be set as eight in or eight out Data is written to and read from this port in bytes If programmed for output a write to this register will update the outputs A zero sets the output to TTL Low A one sets the output to TTL High NOTE TT
Download Pdf Manuals
Related Search