Specification
NET2272 USB Peripheral Controller
______________________________________________________________________________
NetChip Technology, Inc., 2003
Patent Pending
335 Pioneer Way, Mountain View, California 94041
TEL (650) 526-1490
FAX (650) 526-1494
http://www.netchip.com
Rev 1.2, October 15, 2003
22
4.5
I/O Transactions
I/O transactions are those in which a CPU on the local bus accesses registers or packet buffers within the NET2272.
4.5.1 Non-Multiplexed I/O Read
Non-multiplexed I/O read transactions are started when both CS# and IOR# are asserted. The address must be valid
T4 before CS# and IOR# are both asserted. Valid read data is driven onto the data bus within T6 after CS# and
IOR# are both asserted. The read transaction ends and the data bus floats when either CS# or IOR# are de-asserted.
A new I/O read transaction cannot be started until the T8A recovery time has expired, and a new I/O write
transaction cannot be started until the T8B recovery time has expired. ALE must be held low for non-multiplexed
mode.
A0
D0
NetChip Technology; NET2272; Non-Multiplexed I/O Read; 8/19/02; IORD.TD
A1
D1
0ns
25ns
50ns
75ns
LA[4:0]
CS#
IOR#
LD[15:0]
4.5.2 Multiplexed I/O Read
Multiplexed I/O reads are started when the address is driven onto the lower bits of the data bus, and ALE is pulsed.
Once the address has been latched into the NET2272, the data phase is initiated with the assertion of both CS# and
IOR#. To prevent bus contention on the data bus, CS# and IOR# should not be asserted until the local bus master
has tri-stated the address. Valid read data is driven onto the data bus within T6 after CS# and IOR# are both
asserted. The read transaction ends and the data bus floats when either CS# or IOR# are de-asserted. A new I/O
read transaction cannot be started until the T8A recovery time, has expired, and a new I/O write transaction cannot
be started until the T8B recovery time has expired.
D0
NetChip Technology; NET2272; Multiplexed I/O Read; 08/19/02; IORD_MPX.TD
D1
A0
A1
0ns
25ns
50ns
75ns
100ns
ALE
CS#
IOR#
LD[15:0]
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