Owner's manual
24 ©Copyright 2005 Cirrus Logic, Inc. DS651UM23
Version 2.3
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 CS1810xx/CS4961xx when HREQ
is low and can
write data to CS1810xx/CS4961xx when HREQ
is high.
7.2 Host Port Timing - Motorola
®
Mode
(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 HRW high t
mdd
-19ns
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
-18ns
HEN
or HDS high to HEN and HDS low for next read t
mrd
30 - ns
HEN
or HDS high to HEN and HDS low for next write t
mrdtw
30 - ns
HR/W
rising to HREQ falling
t
mrwirqh
-12ns
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
HRW
setup before HEN and HDS low t
mrwsu
24 - ns
HRW
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 HRW high for
next read
t
mwtrd
30 - ns
HEN
or HDS high to HEN and HDS low for next write t
mwd
30 - ns
HRW
rising to HREQ falling
t
mrwbsyl
-12ns