DESCRIPTION OF PIN FUNCTIONS
PLCC
PIN NO.
69
NAME
nI/O 16-Bit
Chip Select
SYMBOL
nIOCS16
DESCRIPTION
Output. This active low signal is used to indicate that the
present data transfer is a 16-bit I/O cycle. A15-A2 are
used to generate nIOCS16. This is an open-drain signal.
An external pull-up resistor is typically provided by the
system.
Input. This active low signal is used to enable the
COM90C66 to transfer data on D8-D15 of the Data Bus.
Output. These active low signals carry the transmit data
information, encoded in pulse format, from the
COM90C66 to the LAN Driver.
Input. This signal carries the receive data information
from the LAN Driver to the COM90C66.
MISCELLANEOUS
51-47
Memory Base MS0-MS4
Address Select
Input. These signals are generated by external switches.
They are used by the memory decoder to select a block
of memory. These signals are connected to weak
internal pull-up resistors.
Input. These signals are generated by external switches.
They are used by the I/O decoder to select a block of 16
I/O locations. These signals are connected to weak
internal pull-up resistors.
Input. These signals are generated by external switches.
The Node ID code represents the node identification of
this particular COM90C66. These signals are connected
to weak internal pull-up resistors.
Output.
This active low signal is used for direct
connection to an LED through a resistor to V
cc
to indicate
transmit activity. This signal has 12mA sink capability.
Output.
This active low signal is used for direct
connection to an LED through a resistor to V
cc
to indicate
board activity. This signal has 12mA sink capability.
73
nSystem Bus
High Enable
nPulse 2,
nPulse 1
Receive In
nSBHE
TRANSMISSION MEDIA INTERFACE
56, 55
nPULSE 2,
nPULSE 1
RXIN
57
46-44
I/O Base
IOS0-IOS2
Address Select
35-42
Node ID Select NID0-NID7
32
nTransmit
Activity LED
nBoard Select
Activity LED
nTXLED
31
nnBSLED
6
SMSC [ SMSC CORPORATION ]
