Seagate Ultra 320 - Manual (Page 79)

Parallel SCSI Interface Product Manual, Rev. A 65
2. read the value of the P_CRCA signal within one pCRC receive hold time of the transition of the REQ
signal; and
3. respond with an ACK transition.
If the I/O signal is false (i.e., transfer to the target), to transfer the data field, the initiator:
1. shall wait until after detecting a REQ transition with P_CRCA negated;
2. shall drive the DB(15-0) signals to their values;
3. shall delay at least one transmit setup time;
4. shall transition the ACK signal;
5. shall hold the DB(15-0) signals valid for at least one transmit hold time;
6. may then change or release the DB(15-0) signals; and
7. shall not change the ACK signal for at least one
transmit assertion period if asserted or one transmit
negation period if negated.
If the I/O signal is false (i.e., transfer to the target), to receive the data field, the target:
1. shall read the value of the DB(15-0) signals within one receive hold time of the transition of the ACK.
3.5.2.2.2.1 Data group pad field and pCRC field transfer to SCSI initiator port
The target detects a pad field is required if the I/O signal is true (i.e., transfer to the initiator), the target has
completed the data field transfer of the current data group, and REQ signal is asserted. In this case, the target
shall:
1. wait at least one pCRC transmit hold time since the last REQ assertion to assert P_CRCA;
2. wait at least one transmit hold time since the last REQ assertion to assert the DB(15-0) signals to their
pad values;
3. wait at least the longer of one pCRC transmit setup time from the assertion of P_CRCA or one transmit
setup time from DB(15-0) being driven with valid pad data;
4. wait until the initiator has responded with all ACK transitions for the previous data group;
5. wait at least one transmit REQ assertion period with P_CRCA transitioning since the last REQ asser-
tion;
6. negate the REQ signal without waiting for the ACK transition corresponding to the previous REQ tran-
sition unless the negotiated offset would be exceeded;
7. hold the DB(15-0) signals valid for a minimum of one transmit hold time and hold the REQ signal
negated for a minimum of one transmit negation period;
8. drive the DB(15-0) signals to their pCRC values;
9. wait at least one transmit setup time;
10.assert the REQ signal without waiting for the ACK transition corresponding to the previous REQ transi-
tion unless the negotiated offset would be exceeded;
11. hold the DB(15-0) signals for a minimum of one transmit hold time and hold the REQ signal asserted
for a minimum of one transmit assertion period;
12.drive the DB(15-0) signals to their pCRC values;
13.wait at least one transmit setup time;
14.negate the REQ signal without waiting for the ACK transition corresponding to the previous REQ tran-
sition unless the negotiated offset would be exceeded;
15.hold the DB(15-0) signals for a minimum of one transmit hold time and hold the P_CRCA signal
asserted for at least one pCRC transmit hold time; and
16.hold the REQ signal negated for at least one transmit REQ negation period with P_CRCA transitioning
since the last REQ negation.