If the I/O signal is false (transfer to the target) the target shall request information by asserting the REQ signal. The initiator shall drive the DB(7-0,P) signals to their desired values, delay at least one deskew delay plus a cable skew delay and assert the ACK signal. The initiator shall continue to drive the DB(7-0,P) signals until the REQ signal is false. When the ACK becomes true at the initiator, the initiator may

change or release the DB(7-0,P) signals and shall negate the ACK INTERFACE signal. After the ACK signal is false the target may continue the

transfer by asserting the REQ signal, as described above.

Synchronous Data Transfer

Synchronous data transfer is optional and is only used data phases. It shall be used in a data phase if a synchronous data transfer agreement has been established (see SYCHRONOUS DATA TRANSFER REQUEST Message). The agreement specifies the REQ/ACK offset and the minimum transfer period.

The REQ/ACK offset specifies the maximum number of REQ pulses that can be sent by the target in advance of the number of ACK pulses received from initiator, establishing a pacing mechanism. If the number of REQ pulses exceeds the number of ACK pulses by the REQ/ACK offset, the target shall not assert the REQ signal until after the leading edge of the next ACK pulse is received. A requirement for successful completion of the data phase is that the number of ACK and REQ pulses be equal.

The target shall assert the REQ signal for a minimum of an assertion period. The target shall then wait at least the greater of a transfer period from the last transition of the REQ signal to true or a minimum of a negation period from the last transition of the ACK signal to false before asserting the ACK signal.

The initiator shall send one pulse on the ACK signal for each REQ pulse received. The ACK signal may be asserted as soon as the leading edge of the corresponding REQ pulse has been received. The Initiator shall assert the ACK signal for a minimum of an assertion period. The initiator shall wait at least the greater of transfer period from the last transition of the ACK signal to true or for a minimum of a negation period from the last transition of the ACK signal to false before asserting the ACK signal.

M3099GX/GH OEM Manual

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