Fujitsu MAW3073 SERIES Specifications page 87

(2) DT synchronous data transfer
When a DT data transfer agreement has been established the target shall only use the DT DATA
IN phase and DT DATA OUT phase for data transfers. The DT synchronous data transfer is
available only when it has been defined between the INIT and TARG by exchanging the
PARALLEL PROTOCOL REQUEST message with each other.
During DT data transfers data shall be clocked on both the assertion and negation of the REQ and
ACK signal lines. References to REQ/ACK transitions in this subclause refer to either an assertion
or a negation of the REQ or ACK signal.
The REQ/ACK offset specifies the maximum number of REQ transitions that shall be sent by the
target in advance of the number of ACK transitions received from the initiator, establishing a
pacing mechanism. If the number of REQ transitions exceeds the number of ACK transitions by
the REQ/ACK offset, the target shall not transition the REQ signal until after the next ACK
transition is received. For successful completion of the DT DATA phase the number of ACK and
REQ transitions shall be equal and both REQ and ACK shall be negated.
Note:
The differences from the ST DATA Synchronous mode are the following: (ST DATA Sync
Mode)
1. Only LVD, up to Fast-80 transfer (up to Fast-20, Fast-40 on LVD)
2. 16 bits transfer only (Either 8 bit or 16 bit transfer is available)
3. MSG signal is asserted (MSG signal negated)
4. P_CRCA, P1 signals are used as Data Group Transfer enabled.
5. Both edges of the REQ / ACK are available in the data transmission (Only trailing edge is
available)
Data group contains three fields. They are Data field, Pad field, pCRC field. The following
description is about each field transfer.
(a) Data Group Data field transfer from TARG to INIT
The TARG specifies the data transfer direction using the I/O signal. When the I/O signal is true,
data is transferred from the TARG to the INIT. And MSG signal determines the kind of DATA
phase. When the MSG signal is true, the DATA phase is DT DATA phase. The following explains
the transmission sequence. The target shall not transition the REQ signal when the P_CRCA signal
is asserted for the current data group until the initiator has responded with all ACK transitions for
the previous data groups.
1) TARG drives the DB(15-0) signals to their desired values and shall negate the P_CRCA
signal.
2) TARG waits at least the longer of a pCRC transmit setup time from the negation of
P_CRCA or a transmit setup time from DB(15-0) signals being driven with valid data.
3) TARG transits the REQ signal and holds the DB(15-0) signals valid for a minimum of a
transmit hold time and the P_CRCA signal for a minimum of a pCRC transmit hold time.
4) TARG holds the REQ signal for at least a transmit assrttion period if asserted or a transmit
negation period if negated.
C141-C011 1-69