Specification
NET2270 USB Interface Controller
______________________________________________________________________________
NetChip Technology, Inc., 2003
335 Pioneer Way, Mountain View, California 94041
TEL (650) 526-1490
FAX (650) 526-1494
http://www.netchip.com
Rev 3.6, April 17, 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 NET2270.
4.5.1 Non-Multiplexed I/O Read
Non-multiplexed I/O reads 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; NET2270; Non-Multiplexed I/O Read; 12/10/02; 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 NET2270, 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 cycle 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; NET2270; Multiplexed I/O Read; 12/10/02; IORD_MPX.TD
D1
A0
A1
0ns
25ns
50ns
75ns
100ns
ALE
CS#
IOR#
LD[15:0]
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