COM20020_00 Datasheet, PDF (5/82 Pages) SMSC Corporation – Universal Local Area Network Controller with 2K x 8 On-Board RAM

DIP PIN
NO.
1-3
4-11
23
22
19
20
PLCC PIN
NO.
DESCRIPTION OF PIN FUNCTIONS
NAME
SYMBOL
DESCRIPTION
MICROCONTROLLER INTERFACE
1-3
Address
A0/nMUX, Input. On a non-multiplexed mode, A0-A2
0-2
A1,A2/ALE are address input bits. (A0 is the LSB) On a
multiplexed address/data bus, nMUX tied
Low, A1 is left open, and ALE is tied to the
Address Latch Enable signal. A1 is
connected to an internal pull-up resistor.
4-6,8-12 Data 0-7
AD0-AD2,
D3-D7
Input/Output. On a non-multiplexed bus,
these signals are used as the data lines for
the device. On a multiplexed address/data
bus, AD0-AD2 act as the address lines
(latched by ALE) and as the low data lines for
the device. D3-D7 are always used for data
only. These signals are connected to internal
pull-up resistors.
27
nRead/nData nRD/nDS Input. On a 68XX-like bus, nDS is an active
Strobe
low signal issued by the microcontroller as the
data strobe signal to strobe the data onto the
bus. On a 80XX-like bus, nRD is an active
low signal issued by the microcontroller to
indicate a read operation.
26
nWrite/
nWR/DIR Input. On a 68XX-like bus, DIR is issued by
Direction
the microcontroller as the Read/nWrite signal
to determine the direction of data transfer. In
this case, a logic "1" selects a read operation,
while a logic "0" selects a write operation. In
this case, data is actually strobed by the nDS
signal. On an 80XX-like bus, nWR is an
active low signal issued by the microcontroller
to indicate a write operation. In this case, a
logic "0" on this pin, when the COM20020 is
accessed, enables data from the data bus to
be written to the device.
23
nReset in
nRESET
Input. This active low signal executes a
hardware reset.
24
nInterrupt nINTR
Output. This active low signal is generated by
the COM20020 when an enabled interrupt
condition occurs.
5
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