LSI Logic Confidential
10-10
Host Async Master Interface
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
since it gives the target device more time to decode the transfer and
assert the M_WAIT signal. The delay is from the start of the cycle to the
beginning of the first possible data phase (the next clock is the first one
in which the data and transfer acknowledge will be sampled). The DT
parameter can also be used to delay the sampling of M_DTACK.
10.4.6 Multiplexed Address Cycles
The DMN-8600 multiplexes the middle address bits 21 to 6 on the
Addr/Data lines. For these cycles, the address bits are captured with an
external latch. An address latch enable pin (M_ALE) is provided to
control the latch.
The address multiplexing feature is selectively enabled on a
per-chip-select basis. This allows the designer to have both large
address space devices (like Flash ROMs) that use the multiplexing and
small address space devices (UARTs, etc.) that do not. The large
address space devices take a small cycle hit in performance per burst,
while the smaller devices are directly addressed by the limited number
of dedicated address pins.
below shows a multiplexed address cycle:
Содержание DMN-8600
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