M27C512
Device operation
2
Device operation
The modes of operations of the M27C512 are listed in the Operating Modes table. A single
power supply is required in the read mode. All inputs are TTL levels except for GV
PP
and
12V on A9 for Electronic Signature.
2.1
Read mode
The M27C512 has two control functions, both of which must be logically active in order to
obtain data at the outputs. Chip Enable (E) is the power control and should be used for
device selection. Output Enable (G) is the output control and should be used to gate data to
the output pins, independent of device selection. Assuming that the addresses are stable,
the address access time (t
AVQV
) is equal to the delay from E to output (t
ELQV
). Data is
available at the output after a delay of t
GLQV
from the falling edge of G, assuming that E has
been low and the addresses have been stable for at least t
AVQV
-t
GLQV
.
2.2
Standby mode
The M27C512 has a standby mode which reduces the active current from 30mA to 100µA
The M27C512 is placed in the standby mode by applying a CMOS high signal to the E input.
When in the standby mode, the outputs are in a high impedance state, independent of the
GV
PP
input.
Table 3.
Operating modes
(1)
Mode
Read
Output Disable
Program
Program Inhibit
Standby
Electronic Signature
1.
E
V
IL
V
IL
V
IL
Pulse
V
IH
V
IH
V
IL
GV
PP
V
IL
V
IH
V
PP
V
PP
X
V
IL
A9
X
X
X
X
X
V
ID
Q7-Q0
Data Out
Hi-Z
Data In
Hi-Z
Hi-Z
Codes
X = V
IH
or V
IL
, V
ID
= 12V ± 0.5V.
Electronic Signature
A0
V
IL
V
IH
Q7
0
0
Q6
0
0
Q5
1
1
Q4
0
1
Q3
0
1
Q2
0
1
Q1
0
0
Q0
0
1
Hex Data
20h
3Dh
Table 4.
Identifier
Manufacturer’s
Code
Device Code
5/22
STMICROELECTRONICS [ STMICROELECTRONICS ]
