Communication system, communication device and flow control method

• US 20080183915A1
• Filed: 01/23/2008
• Published: 07/31/2008
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Iima, Tomofumi
• Granted Patent: US 7,765,335 B2
• Time in Patent Office: Days
• US Class Current: 710/29
• CPC Class Codes: G06F 2205/126 Monitoring of intermediate fill level, i.e. with additional means for monitoring the fill level, e.g. half full flag, almost empty flag
• CPC Class Codes: G06F 5/12 Means for monitoring the fill level; Means for resolving contention, i.e. conflicts between simultaneous enqueue and dequeue operations

Abstract

A communication system complying with SPI-4 Phase 2 standard includes a local device, an opposing device, a first data channel to transfer payload data from the local to the opposing device, a second data channel opposed to the first data channel, and a first status channel to be able to transfer data from the local to the opposing device. The local device periodically outputs buffer status information of a data buffer for storing payload data received over the second data channel to the first status channel. Further, the local device inserts the buffer status information between the payload data according to a priority of the buffer status information in order to output the buffer status information to the first data channel. The opposing device controls to output payload data to the second data channel according to the buffer status information received over the first status channel and the first data channel.

Claims

1. A communication system complying with SPI-4 Phase 2 standard comprising:

a local device;

an opposing device;

a first data channel to transfer payload data from the local device to the opposing device;

a second data channel to transfer payload data from the opposing device to the local device; and

a first status channel to be able to transfer data from the local device to the opposing device,

wherein the local device comprises;

a data buffer being configured to store payload data received over the second data channel;

a buffer status information output unit periodically outputting buffer status information to the first status channel, the buffer status information indicating a usage status of the data buffer; and

a buffer status information insert unit inserting the buffer status information between the payload data according to a priority of the buffer status information in order to output the buffer status information to the first data channel,

wherein the opposing device controls to output payload data to the second data channel according to the buffer status information received over the first status channel and the first data channel.

2. The communication system according to claim 1, wherein the opposing device comprises:

a buffer status information receive unit receiving the buffer status information via the first status channel;

a buffer status information extract unit extracting the buffer status information from data received over the first data channel; and

a data output unit being able to suspend outputting payload data to the second data channel according to the buffer status information received by the buffer status information receive unit and the buffer status information extract unit.

3. The communication system according to claim 1, wherein the insertion of the buffer status information between the payload data is performed in response to an excess of an amount of data stored in the data buffer over a predetermined threshold.

4. The communication system according to claim 1, wherein the buffer status information insert unit inserts identification information identifying the data buffer to the payload data, in addition to the buffer status information.

5. The communication system according to claim 1, wherein the insertion of the buffer status information between the payload data is periodically performed.

6. The communication system according to claim 1, wherein a transmission amount for each unit time of the buffer status information inserted to the payload data is larger than a transmission amount for each of the unit time of the buffer status information output to the first status channel.

7. The communication system according to claim 1, wherein the number of the status of the data buffer identifiable by the buffer status information inserted to the payload data is larger than the number of the status of the data buffer identifiable by the buffer status information output to the first status channel.

8. The communication system according to claim 1, wherein the buffer status information includes a buffer address and buffer accumulation information indicating a usage status of the data buffer, and

the buffer status information insert unit allocates the buffer address and the buffer accumulation information to an extension control in order to transfer the buffer status information.

9. A communication device complying with SPI-4 Phase 2 standard to transmit and receive data with an opposing device, the communication device comprising:

a data transmission port to transmit payload data to the opposing device;

a data receive port to receive payload data from the opposing device;

a data buffer to store payload data received from the data receive port;

a status transmission port provided to periodically transmit buffer status information indicating a usage status of the data buffer to the opposing device, the status transmission port having a data transmission rate lower than the data transmission port;

a buffer status information output unit outputting the buffer status information to the first status signal port; and

a buffer status information insert unit inserting the buffer status information between the payload data in order to output the buffer status information to the data transmission port.

10. The communication device according to claim 9, wherein the buffer status information insert unit inserts the buffer status information between the payload data in case an amount of data stored in the data buffer exceeds a predetermined threshold.

11. The communication device according to claim 9, wherein the buffer status information insert unit determines whether or not to insert the buffer status information between the payload data according to a priority of the buffer status information.

12. The communication device according to claim 9, wherein the buffer status information insert unit inserts identification information identifying the data buffer to the payload data, in addition to the buffer status information.

13. The communication device according to claim 9, wherein a transmission amount for each unit time of the buffer status information inserted to the payload data is larger than a transmission amount for each of the unit time of the buffer status information transmitted from the status transmission port.

14. The communication device according to claim 9, wherein the number of the status of the data buffer identifiable by the buffer status information inserted to the payload data is larger than the number of the status of the data buffer identifiable by the buffer status information transmitted from the status transmission port.

15. A method of flow control in a communication system complying with SPI-4 Phase 2 standard including a local device, an opposing device, a first data channel to transfer payload data from the local device to the opposing device, a second data channel to transfer payload data from the opposing device to the local device and a first status channel to be able to transfer data from the local device to the opposing device, the method comprising:

transmitting, by the local device, buffer status information indicating a usage status of a data buffer periodically to the first status channel, the data buffer storing payload data received over the second data channel;

inserting, by the local device, the buffer status information between the payload data according to a priority of the buffer status information and outputting to the first data channel; and

controlling, by the opposing device, to output payload data to the second data channel based on the status information received over the first status channel and the first data channel.

16. The method according to claim 15, wherein the insertion of the buffer status information between the payload data by the local device is performed in response to an excess of an amount of data stored in the data buffer over a predetermined threshold.

17. The method according to claim 15, wherein the local device determines whether or not to insert the buffer status information between the payload data according to a priority of the buffer status information.

18. The method according to claim 15, wherein the local device inserts identification information identifying the data buffer to the payload data, in addition to the buffer status information.

19. The method according to claim 15, wherein a transmission amount for each unit time of the buffer status information inserted to the payload data is larger than a transmission amount for each of the unit time of the buffer status information output to the first status channel.

20. The method according to claim 15, wherein the number of the status of the data buffer identifiable by the buffer status information inserted to the payload data is larger than the number of the status of the data buffer identifiable by the buffer status information output to the first status channel.