M87C257 STMICROELECTRONICS [STMicroelectronics], M87C257 Datasheet - Page 8

• Manufacturer Part Number: M87C257
• Description: ADDRESS LATCHED 256K 32K x 8 UV EPROM and OTP EPROM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M87C257
Figure 6. Programming and Verify Modes AC Waveforms
Figure 7. Programming Flowchart
8/13
YES
NO
FAIL
= 25
++n
V CC
A0-A14
Q0-Q7
ASV PP
E
G
V CC = 6.25V, V PP = 12.75V
CHECK ALL BYTES
NO
2nd: V CC = 4.2V
E = 100 s Pulse
1st: V CC = 6V
VERIFY
n = 0
Addr
Last
YES
YES
tVCHEL
tVPHEL
NO
tQVEL
tAVEL
tELEH
DATA IN
++ Addr
PROGRAM
AI00760B
VALID
tEHQX
PRESTO II Programming Algorithm
PRESTO II Programming Algorithm allows to pro-
gram the whole array with a guaranteed margin, in
a typical time of 3.5 seconds. Programming with
PRESTO II involves the application of a sequence
of 100 s program pulses to each byte until a correct
verify occurs (see Figure 7). During programming
and verify operation, a MARGIN MODE circuit is
automatically activated in order to guarantee that
each cell is programmed with enough margin. No
overprogram pulse is applied since the verify in
MARGIN MODE provides necessary margin to
each programmed cell.
Program Inhibit
Programming of multiple M87C257s in parallel with
different data is also easily accomplished. Except
for E, all like inputs including G of the parallel
M87C257 may be common. A TTL low level pulse
applied to a M87C257’s E input, with V
will program that M87C257. A high level E input
inhibits the other M87C257s from being pro-
grammed.
Program Verify
A verify (read) should be performed on the pro-
grammed bits to determine that they were correctly
programmed. The verify is accomplished with G at
V
IL
tQXGL
, E at V
VERIFY
tGLQV
DATA OUT
IH
, V
PP
at 12.75V and V
tGHQZ
tGHAX
AI00557
CC
at 6.25V.
PP
at 12.75V,