Method of data communication flow control in a data processing system using busy/ready commands

• US 6,157,967 A
• Filed: 12/30/1997
• Issued: 12/05/2000
• Est. Priority Date: 12/17/1992
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Tandem Computers Incorporated (HP Inc.)
• Inventors: Baker, William Edward, Whiteside, Patracia L., Zalzala, Linda Ellen, Garcia, David J., Horst, Robert W., Krause, John C., Cutts, Richard W. Jr., Low, Stephen G., Watson, William Joel, Bunton, William Patterson, Sonnier, David Paul
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): WANG, ALBERT C
• Application Number:
  US09/001,100
• Time in Patent Office: 1,071 Days
• Field of Search: 709/232, 370/236, 370/503, 714/4, 714/10, 710/19
• US Class Current: 710/19
• CPC Class Codes: G06F 15/17381 Two dimensional, e.g. mesh, torus

Abstract

A multiprocessor system includes a number of sub-processor systems, each substantially identically constructed, and each comprising a central processing unit (CPU), and at least one I/O device, interconnected by routing apparatus that also interconnects the sub-processor systems. A CPU of any one of the sub-processor systems may communicate, through the routing elements, with any I/O device of the system, or with any CPU of the system.

Communications between I/O devices and CPUs is by packetized messages. Interrupts from I/O devices are communicated from the I/O devices to the CPUs (or from one CPU to another CPU) as message packets.

CPUs and I/O devices may write to, or read from, memory of a CPU of the system. Memory protection is provided by an access validation method maintained by each CPU in which CPUs and/or I/O devices are provided with a validation to read/write memory of that CPU, without which memory access is denied.

Claims

1. In a processing system comprising at least a pair of transmitting/receiving elements coupled to one another by a bi-directional link for communicating multi-bit words, including multi-bit data words and multi-bit command words, a method of data communication flow control that includes the steps of:

providing each of the pair of transmitting/receiving elements with a transmit clock signal that defines clock periods and is sent on the bi-directional link to the other of the pair transmitting/receiving elements;

a one of the pair of transmitting/receiving elements communicating data in the form of a series of multi-bit data words to the other of the pair of transmitting/receiving devices, each of the multi-bit data words being communicated with a clock period;

in absence of communicating data, the one of the pair of transmitting/receiving elements transmitting with each clock period first multi-bit command words to the other of the pair of transmitting/receiving elements; and

the one of the transmitting/receiving elements periodically sending a BUSY command word to indicate to the other of the pair of transmitting/receiving elements to at least temporarily halt communicating data or, if no data is being communicated, to not communicate data until a READY command word is sent by the one of the transmitting/receiving elements;

wherein after receiving the BUSY command word, failure to receive the READY command word or a subsequent BUSY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

2. The method of claim 1, wherein the first multi-bit command words indicate that no data is being sent.

3. The method of claim 1, wherein the first multi-bit command words include a FILL command word to indicate that communication of the series is not complete.

4. The method of claim 1, including the step of the other of the pair of transmitting/receiving elements transmitting, while receiving the series, second multi-bit command words to the one transmitting/receiving element.

5. The method of claim 4, wherein the second multi-bit command words include a BUSY command word that indicates to the one transmitting/receiving element a request to suspend communication of the series.

6. The method of claim 5, wherein the BUSY command word is later followed by a READY command word that indicates to the one transmitting/receiving element that the other transmitting/receiving element is in a condition to receive data.

7. The method of claim 6, wherein failure to receive the READY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

8. The method of claim 5, wherein failure to receive the BUSY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

9. The method of claim 1, wherein the first multi-bit command words include an IDLE command word to indicate absence of data communication.

10. Apparatus for communicating information in the form of multi-bit data and command symbols, comprising:

at least a pair of transmitting/receiving units each including a transmitting port from which information is transmitted, and a receiving port whereat information is received;

a communications link connecting the transmitting and receiving ports of a one of the pair of transmitting/receiving units to the receiving and transmitting ports, respectively, of the other of the pair of transmitting/receiving units;

the pair of transmitting/receiving units each operating to communicate information to one another in the form of one or more multi-bit command and data symbols or, in absence of either, a first command symbol, the transmitting/receiving units indicating an error if a data or a command symbol is not received within a predetermined period of time;

each of the transmitting/receiving units including means for sending from the transmitting port a BUSY command symbol when receiving information at the receiving port for indicating a temporary cessation of the communication of the information and to periodically send the BUSY signal to maintain the temporary cessation, and for sending a READY command symbol is sent in place of the BUSY command symbol to indicate termination of the temporary cessation and readiness to resume communication of the information.

11. The method of claim 10, wherein failure to receive the BUSY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

12. The method of claim 11, wherein failure to receive the READY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

13. The apparatus of claim 10, wherein the error is indicated when the BUSY command symbol is not received within a predetermined amount of time since receipt of an immediately preceding command symbol.

14. In a processing system comprising at least a pair of transmitting/receiving elements coupled to one another by a bi-directional link for communicating multi-bit words, including multi-bit data words and multi-bit command words, a method of data communication comprising the steps of:

providing each of the pair of transmitting/receiving elements with a transmit clock signal that defines clock periods and is sent on the bi-directional link to the other of the pair transmitting/receiving elements;

a one of the pair of transmitting/receiving elements communicating data in the form of a series of multi-bit data words to the other of the pair of transmitting/receiving devices, each of the multi-bit data words being communicated with a clock period;

in absence of communicating data, the one of the pair of transmitting/receiving elements transmitting with each clock period first multi-bit command words to the other of the pair of transmitting/receiving elements;

the one of the transmitting/receiving elements periodically sending a BUSY command word to indicate to the other of the pair of transmitting/receiving elements to at least temporarily halt communicating data or, if no data is being communicated, to not communicate data until a READY command word is sent by the one of the transmitting/receiving elements; and

the other of the pair of transmitting/receiving elements transmitting, while receiving the series, second multi-bit command words to the one transmitting/receiving element;

wherein failure to receive the READY command word or the BUSY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

15. The method of claim 14, wherein the second multi-bit command words include a BUSY command word that indicates to the one transmitting/receiving element a request to suspend communication of the series.

16. The method of claim 15, wherein the BUSY command word is later followed by a READY command word that indicates to the one transmitting/receiving element that the other transmitting/receiving element is in a condition to receive data.

17. The method of claim 15, wherein failure to receive the BUSY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

18. The method of claim 16, wherein failure to receive the READY command word within a predetermined period of time by the other of the pair of transmitting/receiving elements is an error.

19. In a processing system comprising at least a pair of transmitting/receiving elements coupled to one another by a bi-directional link for communicating multi-bit words, including multi-bit data words and multi-bit command words, a method of data communication flow control that includes the steps of:

communicating data between the pair of transmitting/receiving elements in the form of a series of multi-bit data words;

transmitting periodic first predetermined multi-bit command words in absence of communicating data;

a one of the pair of transmitting/receiving elements inserting a BUSY command word in the series of multi-bit data words to indicate to the other of the pair of transmitting/receiving element a request to suspend communication of information;

receiving the BUSY command work at the other of the transmitting/receiving elements to begin sending a second predetermined command word;

the one of the transmitting/receiving elements sending a READY command word, after sending the BUSY command word, to indicate a readiness to receive data; and

reporting an error when a multi-bit data word or command word is not received within a predetermined period of time.

20. The method of claim 19, including the step of the one of the pair of transmitting/receiving elements completing sending the series of multi-bit data words and then sending periodic BUSY command words to indicate to the other of the pair of transmitting/receiving element a request to suspend communication of information;

and

receiving the BUSY command word at the other of the pair of transmitting/receiving elements to begin sending a second predetermined command word.

21. The method of claim 19, wherein the step of the one of the transmitting/receiving elements sending the READY command includes inserting a READY command word in the series of multi-bit data words to indicate to the other of the pair of transmitting/receiving elements a readiness to receive data.

22. The method of claim 19, including the step of the one of the pair of transmitting/receiving elements completing sending the series of multi-bit data words and then, if a READY command word has not been sent, sending a series of BUSY command words.

23. A method of controlling communication flow between first and second data-communicating elements interconnected for communicating therebetween multi-bit symbols that includes the steps of:

the first data-communicating element transmitting a first series of multi-bit symbols to the second data-communicating element and receiving from the second data-communicating element a second series of multi-bit symbols;

the second data-communicating element inserting a BUSY multi-bit symbol in the second series of multi-bit symbols;

the first data-communicating element receiving the BUSY multi-bit symbol to halt transmission of the first series of multi-bit symbols and to begin transmission of periodic FILL multi-bit symbols;

the second data-communicating element subsequently sending a READY multi-bit symbol that, when received by the first data-communicating element, causes resumption of the first series of multi-bit symbols; and

the first data-communicating element reporting an error when a multi-bit symbol is not received from the second data-communicating element within a predetermined period of time.

24. The method of claim 23, wherein the step of sending the READY multi-bit symbol includes inserting the READY multi-bit symbol in the second series of multi-bit symbols.

25. A method of controlling data flow between at least first and second communicatively intercoupled data communication devices of a data processing system, the first and second data communication devices operating to send the data in the form of messages, the method including the steps of:

operating the first communication device in a first mode to communicate a data message to the second data communication device;

inserting in the data message a BUSY command, and thereafter periodically sending the BUSY command when no data message is being sent;

receiving at the second communication device the BUSY command to inhibit communicating data to the first communication device;

then sending a READY command from the first communication device to the second communication device; and

receiving the READY command at the second communication device to permit communicating data.

26. The method of claim 25, wherein the data message includes multi-bit words, and including the step of reporting an error if a successive pair of the multi-bit words or a successive pair of the periodically sent BUSY commands are not received within a predetermined period of time.