FUJITSU M3093DG User Manual
Page 52
deskew delay +
cable skew delay
deskew delay
+ cable skew delay
bus settle
delay
BSY
SEL
C/D, MSG
REQ
ACK
DB
I/O
(2)
Synchronous information 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
4.6.2. (13)). 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 munimum
of a negation period from the last transition of the ACK signal to false before
asserting the ACK signal.
4 $ 20