DESCRIPTION OF PIN FUNCTIONS
DIP PIN
NO.
1-3
PLCC PIN
NO.
1-3
NAME
SYMBOL
DESCRIPTION
MICROCONTROLLER INTERFACE
Address
0-2
A0/nMUX,
A1,A2/ALE
Input. On a non-multiplexed mode, A0-A2
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.
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.
Input. On a 68XX-like bus, nDS is an active
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.
Input. On a 68XX-like bus, DIR is issued by
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 COM20019 is
accessed, enables data from the data bus to
be written to the device.
Input. This active low signal executes a
hardware reset.
Output. This active low signal is generated by
the COM20019 when an enabled interrupt
condition occurs.
Input. This active low signal selects the
COM20019 for an access.
5
4-11
4-6,8-12
Data 0-7
AD0-AD2,
D3-D7
23
27
nRead/nData nRD/nDS
Strobe
22
26
nWrite/
Direction
nWR/DIR
19
20
23
24
nReset in
nInterrupt
nRESET
nINTR
21
25
nChip Select
nCS
SMSC [ SMSC CORPORATION ]
