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©
Copyright 2004 Cirrus Logic, Inc.
DS651UM21
Version 2.1
CobraNet Hardware User’s Manual
Host Management Interface (HMI)
HREQ may be wired to a host interrupt or DMA request input. HREQ is used to signal the
host that data is available (read case, logic 0) or space is available in the host port data
channel (write case, logic 1).
The read and write case are distinguished by the HMI based on the preceding message.
Identify, Goto Translation
(read),
Goto Packet
(read) and
Goto Counters
cause HREQ to
represent read status.
Goto Translation
(write) and
Goto Packet
(write) switch HREQ to
write mode. All other commands have no effect on HREQ operation.
In general, the host can read from the CS181xx when HREQ is low and can write data to
CS181xx when HREQ is high.
7.2 Host Port Timing
(C
L
= 20 pF)
NOTES:1. The system designer should be aware that the actual maximum speed of the communication port may
be limited by the firmware application. Hardware handshaking on the HREQ# pin/bit should be
observed to prevent overflowing the input data buffer.
Parameter
Symbol
Min
Max
Unit
Address setup before HEN# and HDS# low
t
mas
5
-
ns
Address hold time after HEN# and HDS# low
t
mah
5
-
ns
Read
Delay between HDS# then HEN# low or HEN# then HDS#
low
t
mcdr
0
-
ns
Data valid after HEN# and HDS# low with HR/W# high
t
mdd
-
19
ns
HEN# and HDS# low for read
t
mrpw
24
-
ns
Data hold time after HEN# or HDS# high after read
t
mdhr
8
-
ns
Data high-Z after HEN# or HDS# high after read
t
mdis
-
18
ns
HEN# or HDS# high to HEN# and HDS# low for next read
t
mrd
30
-
ns
HEN# or HDS# high toHEN# and HDS# low for next write
t
mrdtw
30
-
ns
HR/W# rising to HREQ# falling
t
mrwirqh
-
12
ns
Write
Delay between HDS# then HEN# low or HEN# then HDS#
low
t
mcdw
0
-
ns
Data setup before HEN# or HDS# high
t
mdsu
8
-
ns
HEN# and HDS# low for write
t
mwpw
24
-
ns
HR/W# setup before HEN# AND HDS# low
t
mrwsu
24
-
ns
HR/W# hold time after HEN# or HDS# high
t
mrwhld
8
-
ns
Data hold after HEN# or HDS# high
t
mdhw
8
-
ns
HEN# or HDS# high to HEN# and HDS# low with HR/W#
high for next read
t
mwtrd
30
-
ns
HEN# or HDS# high to HEN# and HDS# low for next write
t
mwd
30
-
ns
HR/W# rising to HREQ# falling
t
mrwbsyl
-
12
ns