LSI Logic Confidential
Cycle Types
10-9
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
Figure 10.3 Async Master Device-paced Transfer
The external M_DTACK signal is used as an input to generate an internal
M_DTACK signal synchronized to the internal clock. The external
M_DTACK signal is asynchronous, which must be asserted for at least
two rising edges of the internal clock.
As usual, after the internal M_DTACK signal has been active for a clock,
read data is sampled and M_CS and the data strobe signals are
deasserted. The designer must be careful to ensure that the target
device has deasserted M_DTACK before the next cycle samples it
(starting with the clock edge that asserts the data strobes); otherwise, it
may cause premature termination of the following cycle. Typically, this
requires an extension of the BH parameter.
Note that for device-paced burst transfers, the M_DTACK or M_WAIT line
is sampled only for the first beat of the transfer. Subsequent beats use
the BDT timing.
When using device-paced transfers, the DT timing parameter controls the
delay before the master begins sampling M_DTACK or M_WAIT. This is
most useful when the data acknowledge strobe is a M_WAIT signal,
CSO
DSO
BH
DT
M_A
M_RD/WR
M_CS
M_UDS/LDS
M_D
M_DTACK
(External)
M_DTACK
(Internal)
Содержание DMN-8600
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