Fujitsu MBA3147RC Primitives used only inside SSP and SMP connections, ACK acknowledge, Done

SAS Interface

1.4.4 Primitives used only inside SSP and SMP connections

1.4.4.1ACK (acknowledge)

The ACK primitive indicates that an SSP frame is received normally. When a drive receives an SSP frame, and the CRC field in the received SSP frame is correct, the drive sends the ACK primitive within 1 ms.

1.4.4.2CREDIT_BLOCKED

The CREDIT_BLOCKED primitive indicates that no more credits can be sent during this connection. When a drive determines that it can give out no more credits during the connection, the drive sends the CREDIT_BLOCKED primitive to avoid credit timeout. A drive sends the CREDIT_BLOCKED primitive in any of the following cases:

1)When the drive sends an OPEN frame and, then, receives the OPEN_ACCEPT primitive from the initiator during the abort processing in the drive, the drive sends the CREDIT_BLOCKED primitive instead of an RRDY primitive.

2)When the drive determines during the connection that it has entered a condition where abort processing inside the drive is necessary, if an SSP frame is received from the initiator, the drive sends the CREDIT_BLOCKED primitive instead of an RRDY primitive.

After sending the CREDIT_BLOCKED primitive, the drive must wait until the connection is closed before it can send an RRDY primitive.

Meanwhile, when a drive receives the CREDIT_BLOCKED primitive from the initiator, the drive performs any of the following processing:

1)At the time of the receipt of the CREDIT_BLOCKED primitive, if the drive holds credits that have been given before and has frames to send, the drive can send as many frames as there are credits being held at this time.

2)At the time of the receipt of the CREDIT_BLOCKED primitive, if the drive holds credits that have been given before but has no frames to send, the drive sends the DONE (CREDIT TIMEOUT) primitive and starts the close processing.

3)At the time of the receipt of the CREDIT_BLOCKED primitive, if the drive holds no credits, it sends the DONE (CREDIT TIMEOUT) primitive and starts the close processing.

1.4.4.3DONE

A DONE primitive indicates the start of the close processing of an SSP connection. In the close processing, in principle, when no frame for processing remains on the side of the OPEN frame sender (recipient of the OPEN_ACCEPT primitive), a DONE primitive is sent. However, there is no rule concerning which side should first start the close processing.

Table 1.15 contains DONE primitive definitions.

54 C141-C013