lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllIIIIIIIHIII
Contents
1. ESCAPE CODE CHARACTER CHARACTER RECEIVED INCREMENT ESCAPE CHARACTER IS ESCAPE CODE COMPLETE ca i rn RECEIVED 418 ESCAPE FROM TRANSPARENT c c rn Sheet 4 of 4 5 359 648 Oct 25 1994 U S Patent ccG SIWNOIS 1081N09 geg 3dY253 4009 3dv253 CWWVUSOHd 40103130 4009 3jdV253 uO1VEVdWO y ANIA e INWA H0LVHVdWOJ JIL JWI CSWNVH9OUd QSWNVHOOUd s 40104140 H3 H3JLYHYH axl 40133130 J NINDJS 3dV253 XAW IVN9IS TOULNOD ves 103135 TINIIS 904d G SIJ 5 359 648 1 ESCAPE SEQUENCE USING MONITORING OF CONTROL SIGNAL STATES BACKGROUND OF THE INVENTION A Field of the Invention This invention relates to data communication equip ment B Related Art Apparatus which perform data communication oper ations over telephony lines are well known in the art For example it is known to provide a digital telephone 5 with a data communication controller DCC which enables an attached computer to communicate with the digital telephone itself or with another device e g another computer by way of a digital telephony line Where data communication over an analog telephony line is desired a modulator demodulator more com monly known as a modem is used to convert the digital computer generated signals into modulated ana log signals for transmission over the2. US005359648A United States Patent ns 11 Patent Number 5 359 648 Dunn et al 4 Date of Patent Oct 25 1994 54 ESCAPE SEQUENCE USING MONITORING OF CONTROL SIGNAL STATES FOREIGN PATENT DOCUMENTS 0457704 11 1991 European Pat Off 375 8 75 Inventors Tave P Dunn Elie A Jreij both of Austin Tex Richard M Ludwin OTHER PUBLICATIONS Poughkeepsie N Y William E ROLMphone User s Manual pp 11 4 to 11 10 Levene Austin Tex I Primary Examiner Curtis Kuntz 73 Assignee Rolm Company Santa Clara Calif Assistant Examiner Jason Chan Di Appl No 997 995 57 ABSTRACT A method and apparatus for escaping from transparent 22 Filed Dec 28 1992 mode in which the Data Communication Equipment will escape from transparent mode into command 51 Int CLS H04M 11 00 HO4L 5 16 mode if a user programmed escape character string is 52 U S Ch 379 93 379 94 received in coincidence with the toggling of a control 375 8 signal such as Request To Send RTS Advanta 58 Field of Search 379 93 94 96 99 geously this escape method can be used in conjunction 379 98 375 8 9 121 104 114 with time data escape methods that are based soley on activity on the received data line When the two meth 56 References Cited a ods are used together a supervisor program or control U S PATENT DOCUMENTS device can force an escape notw
3. analog telephony lines A modem at a receiving station demodulates the analog signals and converts them back into digital form for use by a digital device at the receiving end of the telephony line DCCs and modems typically have two modes of operation a transparent mode in which digital data from the sending device is passed through to the tele phony lines in analog form in the case of a modem and a command mode in which the DCC or modem will accept commands from the sending device For exam ple while in command mode the sending device may have the DCC dial a number or select an incoming or outgoing line on the digital telephone The prior art includes a number of ways of switching between transparent mode and command mode For example it is known in the art to have a modem switch from transparent mode to command mode upon recog nition of a predefined escape sequence The escape sequence may take a number of forms For example the escape sequence may take the form a non printable character such as Ctrl X the X key depressed along with the Ctrl key One problem with such escape sequences is that while in transparent mode if a sequence of characters matching the escape sequence happens to appear in the transmitted character stream the DCC or modem may undesirably or unexpectedly change from the transpar ent mode to the command mode Thus in DCCs or modems where it is desired to transmit the escape se
4. communication command processor 124 The data communication command processor con trols the DCC in response to commands in accordance with the conventional AT command set with exten sions for activating the telephony command proces sor s The telephony control processor 121 handles the telephony protocol that is received from the telephony network link It interprets and responds to telephony commands such as LED cadence commands and ISDN call status events In addition the telephony control processor 121 sends information from the telephone to the link such as information resulting from key depres sions The telephony command processor 122 handles tele phony commands Like the data communication com mands the telephony commands are sent by a con nected apparatus via an RS 232 port Once in command mode a user can activate the telephony command pro cessor set by keying the proper AT command sequence e g AT U The telephony command processor can include more than one telephony command set each of which can be entered by way of a distinct AT com mand A computer workstation 126 can be coupled to either of the DCC s communication ports 114 116 by way of its own RS 232 data communication port 128 An appli cation program 130 executing on the workstation 126 can send commands and data to the DCC via the work station s RS 232 port 128 In accordance with the RS 232 standard the connection between the workstation
5. communication port and the DCC communication port 15 20 25 30 35 40 45 50 55 60 65 4 includes data lines 107 which carry transmitted and received data and control lines 109 which carry the RS 232 control signals such as Data Terminal Ready Data Set Ready Clear To Send and Request To Send The escape sequence of the present invention can be implemented in a number of different ways According to a first embodiment as illustrated in FIG 2 when the data terminal equipment DTE wants to cause the Data Communication Equipment to escape from transparent mode it first switches the RTS signal from ON to OFF Step 202 Next while maintaining the RTS signal in the OFF state the DTE sends a predetermined se quence of characters the escape code over the trans mit signal line Step 204 Finally after the last charac ter in the escape sequence has been transmitted and before any additional characters are transmitted the DTE switches the RTS signal from OFF to ON Step 206 0f course the above description implies that the RTS signal must be ON before and after transmission of the escape sequence A timing diagram of the above described escape se quence showing the toggling of the RTS signal 302 is illustrated in FIG 3 Characters on the DTE s transmit ted data line TxD are indicated by reference numerals 304 306 and 308 Before the RTS signal 302 drops to the OFF low state data 304 is sent o
6. the above described escape se quence can be used as an alternate escape sequence in conjunction with a time data based escape sequence For example the DCE can be programmed to escape when the escape code is preceded and or followed by a predetermined user programmed time period of no characters 0R when RTS is toggled in coincidence with reception of the escape code as described above A functional block diagram for such an embodiment is illustrated in FIG 5 A character detector 502 produces a pulse each time a character has been received on the DCE s RxD line The pulse from the character detector 502 resets and starts a timer 504 which is in turn connected to a com parator 506 The comparator 506 compares the time between character transmissions with a first user pro grammed time value which is stored within a first regis ter 508 When the time between characters equals or exceeds the first user programmed time value it pro duces a signal which enables turns on an escape code detector 510 The escape code detector monitors the RxD line and produces a pulse when a string of re ceived characters matches a user programmed escape character sequence which is stored in a second register 512 The pulse from the escape code detector resets and starts a second timer 514 It is noted here that the escape 10 15 20 25 30 35 40 45 50 55 60 65 6 code detector resets and turns itself OFF if the escape
7. RTS to monitor for the escape The output of the escape sequence detector 522 is connected to the second input of the OR gate 520 Thus when either escape sequence is detected the toggling of a control signal in conjunction with reception of the escape data OR the escape data immediately preceded and suc ceeded by a predetermined period of time during which no characters are received the DCE will escape from transparent mode and enter command mode As a fur ther modification to the embodiment of FIG 5 two Separate escape sequence character registers can be provided such that the two escape sequences can use different escape character strings It should be understood that the logic of FIG 5 can be embodied in the programming code of the primary microprocessor 102 of FIG 1 Further the mechanism of FIG 5 can include the additional constraint that in order to cause an escape the characters in the escape sequence must arrive separated from one another in time by less than a predetermined period of time The advantage of the embodiment of FIG 5 or its programmed equivalent is that a supervisor program or control hardware can force an escape when needed without regard to and without disturbing the user pro grammed time periods Now that the preferred embodiments have been de scribed various modifications and improvements that do not depart from the scope or spirit of the invention will occur to those of skill in the art Thus it sho
8. ence is transmitted to be detected by the escape mechanism The operation of the Data Communication Equip ment the DCC in the presently described embodiment is illustrated in FIG 4 From the perspective of the Data Communication Equipment the RTS signal is perpetu ally monitored during character transmissions RTS must first be ON before any escape can be detected When RTS is detected to be ON step 402 the escape detection mechanism is armed and an escape character counter is reset step 404 While monitoring the RTS signal step 406 the escape detection mechanism moni tors the transmitted data line TxD for incoming char acters from the DTE step 408 If a character is re 5 359 648 5 ceived it is compared to the specified escape code step 410 If the character matches an escape code character then the escape character counter is incremented step 411 If the complete escape code has not been received step 412 the detection mechanism resumes monitoring of RTS and TxD steps 406 and 408 If the character checked in step 410 is not part of the escape code then the escape fails the DCE remains in transparent mode and the detection mechanism returns to step 402 to wait for RTS to be ON again Once the escape code is determined to be complete step 412 the detection mechanism waits for RTS to be ON step 414 If any character is received before RTS is ON step 416 then the escape fails the DCE remains in transpar
9. ent mode and the detection mechanism re turns to step 402 to wait for RTS to be ON again If in step 414 it is determined that RTS has been turned on before any further characters have been received on the TxD line the escape is considered to be complete and the DCE switches to command mode step 418 It should be understood that the escape code need not be a repetition of the same character In embodiments where a nonrepetitive escape code such as ABC can be chosen step 410 will also check to ensure that the escape characters are received in proper sequence If an escape character is received out of sequence the detec tion mechanism will return to step 402 The present escape sequence can be generated in a number of different ways In one embodiment a call able program the escape program 132 is provided in the workstation 126 to toggle RTS and send the escape sequence in the appropriate timing The escape program can then be called by an application program or the operating system supervisor program 131 whenever an escape from transparent mode needs to be accom plished Further the operating system 131 or applica tion program 130 can be set up to call the escape pro gram in response to user depression of a predetermined key or keys on a keyboard 134 As an alternative em bodiment the appropriate communication port control instructions can be embedded directly into the supervi sor or user program Advantageously
10. er Transmitter UART The primary microprocessor 102 e g a Motorola 68302 is connected to the internal data bus 103 of a conventional digital telephone not shown the secondary microprocessor 104 a set of RS 232 transceivers 106 a random access memory RAM 108 and a read only memory ROM 110 The secondary microprocessor 104 e g a Motorola 6805 is connected to the primary microprocessor 102 the control bus 105 of the conventional digital tele phone and a second set of transceivers 112 The trans ceivers 106 112 are in turn respectively connected to a first RS 232 port PORT1 114 and a second RS 232 port PORT2 116 The secondary microprocessor 104 serves as a conduit between the primary microprocessor 102 and the control bus 105 and second RS 232 port 116 The secondary microprocessor 104 includes inter nal code to pass ISDN call status events received from the network via the control bus 105 to the primary microprocessor 102 and to pass commands and re sponses between the second RS 232 port 116 and the primary microprocessor 102 5 359 648 3 The RAM 108 provides workspace for the primary microprocessor and includes a data buffer area for the RS 232 ports The ROM 110 includes a number of pro grams subroutines or processes which are executed by the primary microprocessor 102 These processes in clude a data transfer processor 120 a telephony control processor 121 a telephony command processor 122 and a data c
11. ges of the at least one control signal occur in coincidence with reception of the prede termined sequence of data 2 The apparatus of claim 1 wherein the reception means comprises a user programmable multiplexor con nected to receive a plurality of control signals from the utilization device the multiplexor being operative to output a user selected one of the control signals to the coincidence detection means 3 The apparatus of claim 1 wherein the at least one control signal is Request To Send 4 The apparatus of claim 1 wherein the coincidence detection means comprises means for detecting a change of state of the at least one control signal both preceding and succeeding reception of the escape code and without reception of any intervening characters 5 The apparatus of claim 4 wherein the coincidence detection means further detects a change of state of the at least one control signal during reception of the escape sequence 6 The apparatus of claim 5 wherein the at least one control signal is Request To Send 7 In a data communication device DCE including an input port for connecting the data communication device to a utilization device and a telephone port for connecting the DCE to a telephone line the DCE hav ing two distinct modes of operation a transparent mode in which the DCE provides to the telephone port data characters defined by data signals received at the input port and a command mode in which the DCE re spo
12. ithstanding the user 4 549 302 10 1985 Heatherington 375 8 Programmed time constraint parameters in the DCC 4 926 448 5 1990 Kraul et al 375 121 4 928 305 5 1990 Yui eene 375 8 17 Claims 4 Drawing Sheets APPLICATION PROGRAM 13e PROCESSOR WORKING AREA EVENT MASK DATA BUFFERS 130 ESC SEQ PROGRAM SUPERVISOR PROGRAM DATA TRANSFER PROCESSOR DATA COMM COMMAND PROC g 126 C N T TELEPHONY L CONTROL PROC TELEPHONY COMMAND PROC 122 T 116 306 ye ABC DEFG HIJ KLMN XXX ATZ ATOT 5554242 602 Sheet 1 of 4 5 359 648 Oct 25 1994 U S Patent P 9Id Quv08A33 get WVU90Ud YOSTAUAdNS WVU90Ud 035 253 Wvu90dd NOTLVOT lddV 9r Odd ONVWHOO ANOHd3 131 JOtd 081NOJ ANOHd3 131 JOud ONVWHO WWO VIVO 40SS400Ud u34SNvul VIVO u0SS3J0td Sd344ng VIVO X5VW 1N3A3 V3uV 9NDIUOM HOSS300Ud D BO U S Patent Oct 25 1994 Sheet 2 of 4 5 359 648 FIG 2 TURN OFF REQUEST TO SEND RTS TRANSMIT ESCAPE SEGUENCE DATA TURN ON REQUEST TO SEND FIG 3 306 ABC DEFG HIJ KLMN XXX ATZ ATDT 5554242 302 FIG 6 306 gor w ABC DEFG HIJ KLMN XXX _ATZ_ATDT 5554242 602 U S Patent Oct 25 1994 Sheet 3 of 4 5 359 648 FIG 4 RESET ESCAPE CHARACTER COUNTER
13. n nected to receive a plurality of control signals from the utilization device the multiplexor being operative to output a user selected one of the control signals to the coincidence detection means 9 The apparatus of claim 7 wherein the at least one control signal is Request To Send 10 The apparatus of claim 7 wherein the coincidence detection means comprises means for detecting a change of state of the at least one control signal both preceding and succeeding reception of the escape code and without reception of any intervening characters 11 The apparatus of claim 10 wherein the coinci dence detection means further detects a change of state of the at least one control signal during reception of the escape code 12 The apparatus of claim 10 wherein the at least one control signal is Request To Send 13 A Data Terminal Equipment DTE apparatus for use in conjunction with Data Communication Equip ment DCE having an input port and an output port and two distinct modes of operation a transparent mode in which the DCE provides to the output port data characters defined by data signals received at the input port and a command mode in which the DCE responds to the data signals received at the input port as instructions to the DCE the DTE comprising a communication port comprising a control line and at least one data line data transmission means for sending data characters on the at least one data line and escape seque
14. n coincidence with the toggling of a control signal such as Request To Send RTS Advantageously this escape method can be used in conjunction with purely data based escape methods such that a supervisor program or control device can force an escape notwithstanding user programmed time constraint parameters in the DCE BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a functional block diagram of a data com munication device according to an embodiment of the present invention FIG 2 is a flow chart of the operation of Data Termi nal Equipment according to an embodiment of the pres ent invention FIG 3 is a timing diagram of the operation of the data communication device of FIG 1 FIG 4 is a flow chart of the operation of Data Com munication Equipment of FIG 1 and FIG 5 is a logic diagram of an alternative embodi ment of the present invention FIG 6 is a timing diagram of an alternative escape sequence to that of FIG 3 Like reference numerals appearing in more that one figure depict like elements DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning first to FIG 1 a DCC of a type suitable for use with a digital telephone is illustrated A suitable digital telephone is described for example in copend ing application Ser No 07 936 963 filed Aug 28 1992 which is incorporated by reference herein The DCC includes two microprocessors 102 104 each of which includes an internal Universal Asynchronous Recei v
15. n the TxD line and the Data Communication Equipment DCE is in transparent mode After RTS is turned OFF the DTE sends the escape code 306 X XX in the present exam ple on the TxD line Next following the transmission of the escape code and before any additional characters are sent by the DTE the DTE switches the RTS signal 302 to the ON high state In response the DCE switches from transparent mode to command mode and the DTE can begin to send a command sequence 308 on the TxD line FIG 6 is a timing diagram of an alternative escape sequence to that of FIG 3 In the escape sequence of FIG 6 the RTS waveform is toggled during the course of transmission of the escape code 306 As a further alternative embodiment a plurality of control signals such as RTS and DTR can be monitored for one or more state changes in conjunction with reception of the escape code in order to effectuate an escape In order to maintain compliance with the RTS speci fication in the EIA 232 D standard it is preferable that the RTS signal be maintained in the ON state whenever characters other than the escape sequence are being transmitted It should be understood however that in systems which do not strictly follow the EIA 232 D standard the RTS signal can generally be OFF and then turned ON a short time before transmitting the escape sequence In any event the RTS signal must be turned ON for a long enough period of time before the escape sequ
16. nce transmission means for toggling a control signal transmitted on the control line in coincidence with transmission of an escape code on the data line such that the DCE will switch from the transparent mode to the command mode in response thereto 14 The apparatus of claim 13 wherein the DTE in cludes key means for activating the escape sequence transmission means in response to one or more key strokes entered by a user 15 The apparatus of claim 13 wherein the control signal is Request To Send 16 The apparatus of claim 13 wherein the escape sequence transmission means changes the control state signal during transmission of the escape code 17 The apparatus of claim 16 wherein the DTE is a computer workstation and the DCE is an integral part of a digital telephone
17. nds to the data signals received at the input port as instructions to the DCE the DCE including means for defining a predetermined sequence of the data signals as an escape code means for detecting each occurrence of a passage of a predetermined period of time after provision of one of the data signals to the input port the improvement comprising reception means for receiving at least one control signal from the utilization device coincidence detection means for detecting when a predetermined sequence of state changes of the at least one control signal occur in coincidence with reception of the predetermined sequence of data escape control means responsive to the means for detecting and operative when the DCE is in the 15 20 25 30 35 45 50 55 65 8 transparent mode for causing the DCE to switch to the command mode when a the predetermined sequence of state changes of the at least one control signal occur in coincidence with reception of the predetermined sequence of data or b the predetermined sequence of data signals occurs contiguous in time with at least one occurrence of the passage of the predetermined period of time during which none of the data signals are provided to the input port and in an absence of both of conditions a and b causing the DCE to remain in the transparent mode 8 The apparatus of claim 7 wherein the reception means comprises a user programmable multiplexor co
18. ommunication command processor 124 The data transfer processor 120 is a timer driven interrupt routine The timer which can be externally generated or internal to the primary microprocessor runs at a sufficient rate to handle the necessary data transfer speeds on the RS 232 ports and the telephony link The data communication command processor 124 and the telephony control processor 121 run in a main control loop 125 each processing one piece of informa tion if any is present and then passing control to the next process The data communication command processor 124 calls the telephony command processor 122 when ever a user enters a telephony command set described in more detail later The data transfer processor 120 handles normal data transfers between the data bus 103 and the RS 232 com munication ports 114 116 The data transfer processor 120 also includes code for processing the escape se quence which enables a user or applications program connected via an RS 232 port to change the DCC from transparent mode controlled by the data transfer pro cessor to command mode controlled by either the telephony command processor or the data communica tion command processor The data communication command processor 124 handles data communication commands of the type well known in the art The commands are sent by a con nected apparatus e g a workstation via an RS 232 port On power up the DCC defaults to command mode and the data
19. quence characters across the link while in transparent mode special provision is made to distinguish a recep tion from the computer of the escape character se quence which is intended to be retransmitted as data from reception of the same escape character sequence which is intended as a signal for the DCC or modem to switch from transparent mode to command mode The prior art includes a number of mechanisms for delimiting the true escape sequence from a sequence of characters to be retransmitted For example in syn chronous protocols it is known to precede the escape sequence by predefined delimiter characters For asyn chronous transmissions it is known in the art to provide a modem with a mechanism that escapes from transpar ent mode if and only if the escape sequence is preceded and or followed by a predetermined time period during which no characters are transmitted Some escape mechanisms add the additional constraint that in order 25 40 45 50 60 65 2 to cause an escape the characters in the escape se quence must arrive separated from one another in time by less than a predetermined time SUMMARY OF THE INVENTION The present invention comprises a method and appa ratus for escaping from transparent mode According to an embodiment of the present invention the Data Com munication equipment DCE will escape from trans parent mode if the escape character sequence the es cape code is received i
20. sequence is not received as the first set of characters subsequent to its being turned ON The second timer 514 stops counting and resets when a character is received on the RxD line as detected by the character detector 502 A second comparator 516 compares the output of the second timer which mea sures the time between reception of the escape data sequence and the reception of a subsequent character with a second user programmed time value which is stored within a third register 518 The comparator pro duces a signal which indicates when the time between reception of the escape code and the reception of a subsequent character equals or exceeds the second user programmed time value It will be appreciated here that the first predecessor time value need not equal the second successor time value It will also be appreci ated that in embodiments where one always wants the predecessor and successor time values to be equal a single register can be used This signal is provided as one input of a two input OR gate 520 An Escape Sequence Detector 522 monitors for re ception of the escape code in coincidence with toggling of a control signal such as RTS as described with respect to FIGS 2 4 A control MUX 524 is pro grammed by a user via a register 526 to select any one of the RS 232 control signals available on the RS 232 communication lines connecting the DTE and the DCE Thus advantageously a user can select a signal other than
21. uld be understood that the preferred embodiments have been described by way of example and not by way of limita tion The scope of the present invention is defined by the appended claims We claim 1 In a data communication device including an input port for connecting the data communication device to a utilization device and a telephone port for connecting the data communication device to a telephone line the data communication device having two distinct modes 5 359 648 7 of operation a transparent mode in which the data communication device provides data received at the input port to the telephone port and a command mode in which the data communication device responds to the data received at the input port as instructions to the data communication device the data communication device including means for defining a predetermined sequence of data as an escape code the improvement comprising reception means for receiving at least one control signal from the utilization device coincidence detection means for detecting when a predetermined sequence of state changes of the at least one control signal occur in coincidence with reception of the predetermined sequence of data escape control means responsive to the means for detecting and operative when the data communica tion device is in the transparent mode for causing the data communication device to switch to the command mode when the predetermined sequence of state chan
Download Pdf Manuals
Related Search
lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllIIIIIIIHIII