
3-6
Signals
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
3.2.1
Parallel Channel
Writes
A parallel channel write request is made when the L64005 asserts VREQ
LOW. The write remains pending until the rising edge of VVALID signal
writes the data to the chip. The L64005 deasserts VREQ HIGH in
response to the falling VVALID signal, then the controller is free to assert
VVALID HIGH and switch off the data bus.
Similarly, a parallel channel write request is made when the L64005
asserts AREQ LOW. The write remains pending until the rising edge of
AVALID signal writes the data to the chip.The L64005 deasserts AREQ
HIGH in response to the falling AVALID signal, then the controller is free
to assert AVALID HIGH and switch off the data bus.
Parallel channel writes can remain pending indenitely. Normal I/O oper-
ations can continue while a channel write is still pending. A normal I/O
cycle occurs when CS and AS are asserted. During normal I/O the
VVALID and AVALID signals must remain HIGH if the port is in parallel
mode.
Figure 3.2
Parallel Channel
Input Timing
3.2.2
Serial Channel
Writes
The L64005 asserts the VREQ signal when space is available in the
channel buffer. VREQ is deasserted HIGH when the channel is unable
to accept more data. After VREQ is deasserted, the channel can accept
VREQ
CS
VVALID
AS
A[2:0]
D[7:0]
(Video) Channel
Pending Channel Write
(Video)
Channel
Write
WAIT
READ
I/O Write with
Write