NEC PC-8201 Service Manual page 125

MSM81 C55RSlGS
2048-Bit CMOS Static R A M with
1 1 0
Ports and Timer
General
The hlSX181C55RS is a static RAM in combination with 110 ports and timer. for use with
microprocessors. The XlSh18IC55RS is made from silicon-gate CMOS t e c k ~ o l o g y . It
features very low power dissipation of up t o 100
pA
as standby current when not selected.
The MSM81C55 has 2K-bit of static KAh.1. configured as 256
x
8 bits.
The MSh,I81C55RS
has an access time of 400 ns at maximum so that it can be usetl also in the 80C85A systern
without wait states.
T h e hlSh18 1 C55RS has three general purpose I/O ports: two 8-bit porls and one 6-bit port.
rcspectively. ports A. B. and C. Port C is used to enable and set the modes for the other
two ports.
hlSXl8lC55RS also has a 14-bit built-in programmable counterltimer which can be used t o
generate square pulses for timers o r count pulses.
Features
High-speed operation and low power dissipation
RAM configuration of 256 x 8-bit bytes
Single power supply of 3 V t o 6 V
Completely static operation
Built-in address latch circuitry
8-bit programmable 110 ports (ports A and
B)
6-bit prograrnmablc 110 port (port C)
I -!-bit programmable binary counter/timer
!vlultiplexed addressldata buses
40-pin DIP (JlShl8 1C55RS)
44-pin flat package (XIShl81C55CS)
Compatible with Intel 8 155
APX-E- 17