com20020-5 Standard Microsystems Corp., com20020-5 Datasheet - Page 4

• Manufacturer Part Number: com20020-5
• Description: Com20020-5 Ulanc Universal Local Area Network Controller With 2k X 8 On-board Ram
• Manufacturer: Standard Microsystems Corp.

1-3
4-11
23
22
DIP PIN
NO.
1-3
4-6,8-12
27
26
PLCC PIN
NO.
Address
0-2
Data 0-7
nRead/nDat
a
nStrobe
nWrite/
Direction
NAME
DESCRIPTION OF PIN FUNCTIONS
MICROCONTROLLER INTERFACE
A0/nMUX,
A1,A2/ALE
AD0-AD2,
D3-D7
nRD/nDS
nWR/DIR
SYMBOL
4
Input.
signals are directly connected to the low bits
of the host address bus. On a multiplexed
address/data bus, A0/nMUX is tied low, A1
is left open, and A2 is tied to the Address
Latch Enable signal of the host.
connected to an internal pull-up resistor.
Input/Output.
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, this active low
signal is issued by the microcontroller as the
data strobe signal to strobe the data onto
the bus. On a 80XX-like bus, this active low
signal is issued by the microcontroller to
indicate a read operation. In this case, a
logic "0" on this pin, when the COM20020-5
is accessed, enables data from the device to
the
microcontroller.
Input.
issued
Read/nWrite
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, this active low
signal is issued by the microcontroller to
indicate a write operation. In this case, a
logic "0" on this pin, when the COM20020-5
is accessed, enables data from the data bus
to be written to the device.
data
On a 68XX-like bus, this signal is
On a non-multiplexed bus, these
by
bus
the
DESCRIPTION
signal
On a non-multiplexed bus,
to
microcontroller
be
to
determine
read
by
as
A1 is
the
the
the