March 1988
MM54C89/MM74C89 64-Bit TRI-STATE
Random Access Read/Write Memory
É
General Description
The MM54C89/MM74C89 is a 16-word by 4-bit random ac-
cess read/write memory. Inputs to the memory consist of
four address lines, four data input lines, a write enable line
and a memory enable line. The four binary address inputs
are decoded internally to select each of the 16 possible
word locations. An internal address register latches the ad-
dress information on the positive to negative transition of
the memory enable input. The four TRI-STATE data output
lines working in conjunction with the memory enable input
provide for easy memory expansion.
Read Operation: The complement of the information which
was written into the memory is non-destructively read out at
the four outputs. This is accomplished by selecting the de-
sired address and bringing memory enable low and write
enable high.
When the device is writing or disabled the output assumes a
TRI-STATE (Hi-z) condition.
Features
Y
Wide supply voltage range
Guaranteed noise margin
High noise immunity
Low power
3.0V to 15V
1.0V
Address Operation: Address inputs must be stable t pri-
SA
or to the positive to negative transition of memory enable. It
is thus not necessary to hold address information stable for
Y
Y
Y
0.45 V
CC
(typ.)
fan out of 2
driving 74L
more than t after the memory is enabled (positive to neg-
HA
ative transition of memory enable).
TTL compatibility
Y
Y
Y
Low power consumption
Fast access time
100 nW/package (typ.)
e
Note: The timing is different than the DM7489 in that a positive to negative
transition of the memory enable must occur for the memory to be
selected.
130 ns (typ.) at V
10V
CC
TRI-STATE output
Write Operation: Information present at the data inputs is
written into the memory at the selected address by bringing
write enable and memory enable low.
Logic and Connection Diagrams
Dual-In-Line Package
TL/F/5888–2
Top View
Order Number MM54C89
or MM74C89
TL/F/5888–1
TRI-STATEÉ is a registered trademark of National Semiconductor Corporation.
C
1995 National Semiconductor Corporation
TL/F/5888
RRD-B30M105/Printed in U. S. A.