Method of interfacing remote units to a central microprocessor

• US 4,310,896 A
• Filed: 11/13/1979
• Issued: 01/12/1982
• Est. Priority Date: 11/13/1979
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Eichelberger, Charles W., Cutler, Scott E., Haase, Michael A.
• Primary Examiner(s): Shaw, Gareth D.
• Assistant Examiner(s): Heckler, Thomas M.
• Application Number:
  US06/093,683
• Time in Patent Office: 791 Days
• Field of Search: 364/200 MS File, 364/900 MS File, 364/104, 364/400, 364/705, 340/167 R, 340/313, 340/349
• US Class Current: 710/105
• CPC Class Codes: G06F 11/1443 Transmit or communication errors
• CPC Class Codes: G06F 13/368 with decentralised access control
• CPC Class Codes: G06F 13/4269 using a handshaking protocol, e.g. Centronics connection

Abstract

A method for interfacing two remote electronic units uses four lines and a handshaking routine including the steps of: causing the first unit to simultaneously transmit a strobe signal on one of the four lines and a signal representing one bit of the information to be communicated on a second of the four lines, sending the two signals continuously until acknowledged by the second unit; causing the second unit, when it receives these signals, simultaneously to transmit a strobe signal on a third line and a data signal, which may or may not be the same as that on the second line, on the fourth line, the third and fourth signals being transmitted continuously until their receipt is acknowledged; terminating transmission of the first and second signals when the first unit receives the third and fourth signals; and terminating the transmission of the third and fourth signals when the second unit determines that the first and second signals are no longer being transmitted. This routine is used for transmission of each bit of information to be communicated. If desired, a fifth line may be provided to carry a signal by means of which the first unit can reset the second unit so that transmission of the communication can be reinitiated in the event of difficulties.

Claims

1. A method for transmitting N bits of binary information between a first electronic unit over a first transmission interface, a telecommunications line, and a second transmission interface, to a second electronic unit, in accordance with a handshaking routine, N being a positive integer, and said first and second transmission interfaces each comprising a respective set of four lines, said handshaking routine comprising the steps of:

(a) simultaneously transmitting a first strobe signal STROBE 1 and a first data signal DATA 1, respectively, on first and second ones of said four lines of said first transmission interface;

(b) transmitting the information contained in said first data signal DATA 1 over said telecommunications line in the form of a first frequency signal;

(c) converting in said second transmission interface said first frequency signal into a second strobe signal STROBE 2 and a second data signal DATA 2, said second data signal DATA 2 containing the same information as said first data signal DATA 1;

(d) simultaneously transmitting said second strobe and data signals STROBE 2 and DATA 2, respectively, over first and second ones of said four lines of said second transmission interface to said second electronic unit;

(e) simultaneously transmitting from said second electronic unit a third strobe signal STROBE 3 and a third data signal DATA 3 on third and fourth ones of said four lines of said second transmission interface, respectively, information differing from the information contained in said DATA 2 signal;

(f) transmitting the information contained in said DATA 3 signal over said telecommunications line in the form of a second frequency signal;

(g) converting in said first transmission interface said second frequency signal into a fourth strobe signal STROBE 4 and a fourth data signal DATA 4, said fourth data signal DATA 4 containing the same information as said third data signal DATA 3;

3. The method of claim 1, wherein each of said first and second frequency signals transmitted over said telecommunications line is a tone pulse the duration of which denotes the information contained in the respective one of said data signals converted into said tone pulse.

4. The method of claim 1, wherein only one of said DATA 1 and DATA 3 signals contains relevant information during any given repetition of said handshaking routine.

5. The method of claim 1, wherein each of said two transmission interfaces includes a respective fifth transmission line and wherein said electronic unit transmits a RESET signal over said fifth transmission lines to said second electronic unit whenever said second electronic unit is to be initialized.

6. The method of claim 4, wherein said first electronic unit reinitiates transmission of said N bits of binary information after the transmission of said RESET signal.

7. The method of claim 5, wherein said N bits of binary information include an initial eight bits followed by from zero to three blocks of data bits, said initial eight bits including:

two bits that constitute a binary number from zero to three denoting the number of data blocks following said eight bits;

five bits following said two bits and consituting a command word; and

one bit following said five bits, said one bit signifying whether relevant information is to be transferred from said first unit to said second unit or from said second unit to said first unit.

9. The method of claim 7, wherein said first and third predetermined levels are the same.

11. The method of claim 7, wherein only one of said DATA 1 and DATA 2 signals, and only one of said DATA 3 and DAT 4 signals, contains relevant information during any one repetition of said handshaking routine.

12. The method of claim 7, wherein said transmission interface further comprises a fifth transmission line and wherein said first electronic unit and said third electronic unit can each, independently of the other, transmit a RESET signal over said fifth line to said second electronic unit whenever it is desired to initialize said second electronic unit.

13. The method of claim 11, wherein said first electronic unit or said third electronic unit reinitiates transmission of said M or N bits of binary information, respectively, after that unit has transmitted said RESET signal.

14. The method of claim 12, wherein said M bits and said N bits of binary information each include an initial eight bits and each further include a respective number from zero to three of blocks of data bits following said respective initial eight bits, with each initial eight bits including:

two bits constituting a respective binary number from zero to three denoting the number of data bit blocks following said respective initial eight bits;

five bits following said two bits and constituting a respective command word; and

one bit following said five bits, said one bit signifying, respectively, whether relevant information is to be transferred from said first electronic unit to said second electronic unit or from said second electronic unit to said first electronic unit and whether relevant information is to be transferred from said third electronic unit to said second electronic unit or from said second electronic unit to said third electronic unit.

2. (h) simultaneously transmitting said fourth strobe and data signals to said first remote electronic unit, respectively, over third and fourth lines of said first transmission interface to said first electronic unit;

(i) terminating transmission of said first strobe and data signals when said first electronic unit receives said fourth strobe and data signals; and

(j) terminating transmission of said strobe and data signals generated by said second electronic unit when said second electronic unit receives the termination of said first strobe and data signals.

8. A method of transferring M bits of binary information from a first electronic unit to a second electronic unit and N bits of binary information from a third electronic unit to said second electronic unit over a transmission interface including four lines, in accordance with a predetermined handshaking routine, M and N being positive integers, and said handshaking routine comprising the steps of:

(a) simultaneously transmitting from said first electronic unit to said second electronic unit a first strobe signal STROBE 1 and a first data signal DATA 1 on first and second lines of said transmission interface, respectively, at a time when the third and fourth of said four lines of said transmission interface carry signals of first and second predetermined levels, respectively;

(b) when said second electronic unit receives said first strobe and data signals STROBE 1 and DATA 1, simultaneously transmitting from said second electronic unit to said first electronic unit a second strobe signal STROBE 2 and a second data signal DATA 2 on said third and fourth lines of said transmission interface, respectively, with the information contained in said second data signal DATA 2 being the same as that contained in said first data signal DATA 1 if said second electronic unit is not communicating with an electronic unit other than said first unit;

(c) when said second strobe and data signals are detected by said first electronic unit, terminating transmission of said first strobe and data signals STROBE 1 and DATA 1;

(d) when said second electronic unit detects the cessation of said first strobe and data signals STROBE 1 and DATA 1, terminating transmission of said second strobe and data signals STROBE 2 and DATA 2;

(e) simultaneously transmitting from said third electronic unit to said second electronic unit a third strobe signal STROBE 3 and a third data signal DATA 3 over said first and second lines, respectively, of said transmission interface, said transmission being performed at a time when said third and fourth lines of said interface respectively carry signals of third and fourth predetermined levels, respectively;

(f) when said second electronic unit receives said third strobe and data signals STROBE 3 and DATA 3, simultaneously transmitting from said second electronic unit to said third electronic unit a fourth strobe signal STROBE 4 and a fourth data signal DATA 4 on said third and fourth lines of said interface, respectively, the information contained by said fourth data signal DATA 4 being the same as that contained by said third data signal DATA 3 if said second electronic unit is not communicating with an electronic unit other than said third electronic unit;

(g) when said fourth strobe and data signals are detected by said third electronic unit, terminating transmission of said third strobe and data signals STROBE 3 and DATA 3; and

(h) when said second electronic unit detects the cessation of said third strobe and data signals STROBE 3 and DATA 3, terminating transmission of said fourth strobe and data signals STROBE 4 and DATA 4.

10. The method of claim 8, wherein said second electronic unit, when it is not communicating with another electronic unit, applies a signal of said first predetermined level to said third line of said interface and periodically alternates between applying a signal of said second predetermined level and applying said interface.