MULTI FUNCTION POLLING TECHNIQUE

• US 3,725,871 A
• Filed: 02/11/1971
• Issued: 04/03/1973
• Est. Priority Date: 02/11/1971
• Status: Expired due to Term

• Current Assignee: Edward B. Tymann, Richard Nolin, Robert E. Heuttner
• Original Assignee: Edward B. Tymann, Richard Nolin, Robert E. Heuttner
• Inventors: Heuttner, Robert E., Tymann, Edward B., Nolin, Richard
• Primary Examiner(s): Henon, Paul J.
• Assistant Examiner(s): Chirlin, Sydney R.
• Application Number:
  US05/114,431
• Time in Patent Office: 782 Days
• Field of Search: 340/172.5
• US Class Current: 710/109
• CPC Class Codes: G06F 13/22 using successive scanning, e.g. polling G06F13/24 takes precedence
• CPC Class Codes: G06F 13/38 Information transfer, e.g. on bus G06F13/14 takes precedence
• CPC Class Codes: H04L 5/00 Arrangements affording multiple use of the transmission path
• CPC Class Codes: H04L 5/02 Channels characterised by the type of signal

Abstract

Input devices or output devices connected to a common bus of a communications terminal are polled in response to a polling sequence specially coded to request information from either a single input device or number of input devices or status information from either input or output devices. The sequence is transmitted over a communications channel to control apparatus coupled to the bus. The control apparatus stores representations in accordance with the coding of address information items included within the sequence and initiates operations in response to and in correspondence with the stored representations.

Claims

1. A method of polling a plurality of data handling devices of a remote station to process a plurality of different types of requests, said method comprising the steps of:

transmitting to said station first information item signals denoting an address identification of said station, and a designation as to whether said station is to transfer data or supply status information;

transmitting to said station second information item signal denoting an address identification of at least one of said devices, and a designation of whether said device is to transmit or receive data;

receiving said second information item signals at said station, in response to the address identification denoted by said first information item signals;

storing representations of said designation of said received information item signals of said station; and

effecting an operation in said device at said station in response to and in correspondence with said stored representations.

2. The method of claim 1 further including the step of sensing control signals generated by said data handling device identified when said device is to supply status information and transmitting from said station a message indicating that said device is ready to transfer data, is busy and unable to transfer data, or is inoperative.

3. The method of claim 1 wherein said information item signals identifying said device are coded with a predetermined bit configuration for specifying that a plurality of said devices are to supply data.

4. The method of claim 3 wherein said predetermined bit configuration corresponds to a ZERO code.

5. The method of claim 1 wherein said first information item signals define a system addreSs character, As, including a status/data bit, S, and a plurality of station identification bits, At, and said second information items signals define a device address character, Ad, including an input/output bit, I/O, and a plurality of device identification bits, Ad, said As and Ad characters being coded as follows for requesting data from a single addressed data handling device, all input devices, and status information from a single input or output device respectively:

1. At terminal station address, S 0;

Ad not = 0, and I/O 1;

2. At terminal station address, S 0, Ad 0 and I/O ; and

3. At terminal station address, S 1, Ad not = 0 and I/O 1 or 0.

6. The method of claim 5 wherein said As and Ad characters are coded as follows for requesting data be received by a single addressed data handling device:

At terminal station address, S 0, Ad not = 0, and I/O 0.

7. The method of claim 5 wherein said Ad character includes at least one additional bit which is coded as the complement of said input/output bit.

8. The method of claim 5 wherein said As and Ad characters comprise a multicharacter multifunction polling sequence which further includes an end of transmission control character as a first character for initiating said station to a predetermined state and an enquiry control character as a last character.

9. The method of claim 1 further including the steps of :

sensing the presence of a predetermined code; and

, generating a first control signal for inhibiting the transmission of further data characters to a data processing system by said station in response to sensing said predetermined code until said station receives information signals from said data processing system acknowledging said transmission as good.

10. The method of claim 9 further including the steps of:

sensing the number of data characters transmitted to said data processing system; and

, generating a second control signal for inhibiting the transmission of further data characters when a predetermined number of said characters have been transmitted without said sensing of said first control signal until said station receives said acknowledgement signals.

11. The method according to claim 10 further including the steps of:

transmitting information signals denoting address identification of said station and said device for each first group of data characters transferred by a device and each group of data characters in which said first control signal is sensed; and

, inhibiting the transmission of said address identification signals when said second control signal is sensed.

12. The method according to claim 11 wherein said method further includes the steps of:

transmitting an end of text character signals at the end of said data characters in response to said first control signal; and

, transmitting an end of block character signals at the end of each group of data characters in response to each of said second control signals.

13. A method of polling a plurality of peripheral devices of a communications terminal by a remote data processing system to condition a communications control apparatus coupled to said terminal to process a plurality of different types of requests, said method comprising the steps of:

generating a plurality of signals representing an initial message sequence coded to include a first address character for identifying said terminal and for specifying whether said terminal is to transfer data or supply status information, and a second address character coded to specify one or more of said devices, and whether each said device is to transmit or receive data;

transmitting said message sequence to said terminal communicatioNs control apparatus;

receiving said message sequence in response to said first address character according to said message sequence by said control apparatus;

storing the results of said decoding by switching predetermined ones of a plurality of state bistable devices in accordance with said coding;

combining the outputs of said bistable devices so as to define a plurality of procedures for processing said different requests; and

, selecting a predetermined one of said procedures in accordance with the coding of said address information characters.

14. The method of claim 13 wherein said predetermined bit positions of said second address are coded to an unassigned predetermined code for specifying a plurality of devices.

15. The method of claim 14 wherein said predetermined device code is a ZERO code.

16. The method of claim 13 wherein predetermined bit positions within said message sequence are coded so as to be complementary of one another to protect against erroneous decoding of said message characters.

17. The method of claim 13 further including the steps of:

sensing control signals generated by said device interrogated for status; and

, transmitting to said remote data processing system one of a plurality of messages indicating that said device is ready to transfer data, is busy, or is inoperative.

18. The method of claim 17 wherein said plurality of messages for said responses include the following respective character sequences;

DLE, phi , DLE,A, and DLE,B.

19. The method of claim 13 wherein said first address character includes a status/data bit, S, and a plurality of terminal identification bits, At, and said second address character includes an input/output bit, I/O, and a plurality of identification bits, Ad, said first and second characters being coded as follows for specifying a device poll, a system poll and status poll respectively:

1. At terminal address, S 0, Ad device address and I/O, 1;

2. At terminal address, S 0, Ad 0 and I/O 1; and

, 3. At terminal address, S 1, Ad device address and I/O 1 or 0 for specifying either an input device or output device respectively.

20. The method of claim 13 wherein said first and second address characters are coded as follows for specifying a device selection request:

At terminal address, S 0, Ad device address and I/O 0.

21. The method of claim 13 wherein said second address character includes at least one additional bit which is coded as the complement of said input/output bit.

22. The method of claim 13 wherein said first and second characters comprise a multicharacter multifunction polling sequence which further includes an end of transmission control character as a first character of said sequence for initializing said terminal to a predetermined state and an enquiry control character as a last character of said sequence.

23. The method of claim 22 wherein each of said characters of said polling sequence is coded in ASCII code.

24. The method of claim 13 further including the steps of :

sensing the presence of a predetermined code within said data characters being transmitted; and

generating a first control signal for inhibiting the transmission of further data characters from said device to said data processing by said communications control apparatus in response to said predetermined code until said control apparatus receives information signals acknowledging said transmission as good.

25. The method of claim 24 further including the steps of:

sensing by said communications control apparatus the number of data characters transmitted to said data processing system; and

, generating a second control signal for inhibiting the transmission of further data characters when a predetermined number of said characters have been transmitted in the absence of said first control signal until said communications apparatus receives said acknowledgement signals.

26. The method of claim 25 further including the steps of:

transmitting information signals denoting address identification of said terminal and said device by said communications apparatus for each first block of data characters transferred to said apparatus by said device and for each block of said data characters in which said first control signal is sensed; and

, inhibiting the transmission of said address identification signals by said communications control means when said second signal is sensed.

27. The method of claim 26 wherein said address identification signals are transmitted as part of the sequence:

SOH, As and Ad.

28. The method according to claim 26 wherein said method further includes the steps of:

transmitting an end of text character signals at the end of each block in response to said first control signal; and

, transmitting an end of block signal within a series of blocks in response to each of said second control signals.

29. In a remote terminal system including a device scanner control means, a plurality of peripheral devices interconnected through one of a number of device control means to said scanner control means through a common bus, a communications control means for processing different types of polling requests transmitted over a communications channel from a control station defined by an initial message sequence including address characters identifying said terminal system and at least one device, said communications control means being coupled to said channel and said bus, said control means comprising:

decoding means connected to receive and decode each of the characters of said initial sequence in response to said terminal address character, said decoding means including a plurality of bistable storage means for storing indications of the results of decoding and information pertinent to the processing of a specified one of said different types of polling requests transmitted by said control station; and

, receive subcommand generating means coupled to said decoding means for generating control signals to said bus for selectively conditioning said scanner control means and said devices control means for processing said different types of polling requests.

30. The system of claim 29 wherein the state of a first one of said bistable storage means defines a poll request;

the state of a second one of said bistable storage means defines a status poll request;

the state of a third one of said bistable storage means defines a multiple poll request; and

, said communications control means further including a plurality of additional bistable storage means connected to store digital indications of said device address codes in response to predetermined types of said polling requests.

31. The system of claim 30 wherein said first bistable means is switched to a ONE only when a predetermined bit of one of said address characters is set to a predetermined state and said second bistable means is switched to a ONE only when said predetermined bit is set to a state complementary to said predetermined state.

32. The system of claim 30 wherein said third bistable means is switched to its ONE state only when predetermined bit positions of another one of said address characters are set to predetermined states.

33. The system of claim 30 further including a fourth bistable means, said fourth bistable means being switched to a ONE state for defining a selection request only when a predetermined bit position of said second address character is set to a state complementary to the state of said bits for defining said poll requests.

34. The system of claim 32 wherein said predetermined states are all ZEROS.

35. A remote system connected to process different types of polling Requests in the form of an initial message sequence from a central station over a communications channel, said sequence including address characters coded to identify said terminal system and at least one device, said remote terminal system comprising:

a bus including a plurality of data and control lines;

a plurality of peripheral devices;

a plurality of device control means for interconnecting at least one of said devices to communicate with said bus;

a device scanner, said device scanner including address generating means for generating address codes of said plurality of input devices and decoding means coupled to said generating means connected to detect a predetermined character code and condition said address generating means to increment to the address code of a next input device;

a communications control means coupled to said bus and to said communications channel, said communications control means including, decoding means coupled to said communications line and operative to decode each of the address characters of said initial sequence, said decoding means including storage means conditioned to store the results of said decoding and information pertinent to the processing of one of said different types of polling requests, subcommand generating means coupled to said decoding means and being conditioned to generate control signals for processing each of said requests, and bus logic means coupled to said subcommand generating means and to said bus, said bus logic means being conditioned by said generating means to selectively enable said scanner decoding means to condition said address generating means to poll each of the input peripheral devices for data in accordance with a predetermined state of said storage means.

36. In the system of claim 35 wherein predetermined ones of said storage means are in predetermined states to indicate a system poll request.

37. In the system of claim 35 wherein said scanner and device control means each include logic means for switching same to an active state for processing said requests, said communication means being operative in accordance with said state of said storage means to condition said bus logic means to apply a predetermined signal to said bus for inhibiting each of said logic means from switching said scanning means and said device control means to an active state when conditioned to process a status request.

38. The system of claim 37 wherein said bus logic means includes means coupled to said bus for sampling predetermined ones of said bus lines for determining the state of said device polled.

39. In the system of claim 35 wherein said communications means further includes:

memory means coupled to said bus and to said communications line, memory means, said memory means being conditioned by said subcommand generating means during processing of a first type of request to transfer data characters to said communications line from each input device in sequence in response to a complete cycling of said scanner address generating means whereafter said communications means terminates processing of said request.

40. In the system of claim 39 wherein said memory means further includes:

a first addressable storage means including a predetermined number of character locations;

a second addressable storage means including a predetermined number of character storage locations; and

, memory switching means coupled to said first and second storage means, said memory switching means being operative to transfer data characters from an input device to a predetermined one of said storage means, and said memory switching means including logic means coupled to said memory means and to said bus, for sensing when the one of said storage means into which data characters are being written is full and when the other one of said storage means is available, said sensing means being operative to condition said memory switching means to switch storage means for writing data characters into said other storage means whereby said transfers between said bus and said memory storage means and said communications line and said storage means proceed simultaneously.

41. In the system of claim 40 wherein said communications means further includes state control means coupled to said decoding means;

and, message generation means coupled to said decoding means and to said memory switching means, said message generation means being conditioned by said memory switching logic means and state control means to generate information identifying the source of blocks of data characters for each of the first blocks of each block of data characters transferred by each input device for transmission to said central station.