COM90C66 Datasheet, PDF (6/76 Pages) SMSC Corporation – ARCNET Controller/Transceiver with AT Interface and On-Chip RAM

DESCRIPTION OF PIN FUNCTIONS
PLCC
PIN NO.
NAME
SYMBOL
DESCRIPTION
69 nI/O 16-Bit
nIOCS16 Output. This active low signal is used to indicate that the
Chip Select
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.
73 nSystem Bus nSBHE
High Enable
Input. This active low signal is used to enable the
COM90C66 to transfer data on D8-D15 of the Data Bus.
TRANSMISSION MEDIA INTERFACE
56, 55 nPulse 2,
nPulse 1
nPULSE 2,
nPULSE 1
Output. These active low signals carry the transmit data
information, encoded in pulse format, from the
COM90C66 to the LAN Driver.
57 Receive In
RXIN
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.
46-44
I/O Base
IOS0-IOS2
Address Select
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.
35-42
Node ID Select NID0-NID7
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.
32 nTransmit
nTXLED
Output. This active low signal is used for direct
Activity LED
connection to an LED through a resistor to Vcc to indicate
transmit activity. This signal has 12mA sink capability.
31 nBoard Select nnBSLED Output. This active low signal is used for direct
Activity LED
connection to an LED through a resistor to Vcc to indicate
board activity. This signal has 12mA sink capability.
6