M27W801 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'M27W801' PDF : 16 Pages View PDF
Figure 7. Programming and Verify Modes AC Waveforms
M27W801
A0-A19
Q0-Q7
VCC
GVPP
E
tAVEL
DATA IN
tQVEL
VALID
tEHQX
DATA OUT
tEHAX
tEHQZ
tVCHEL
tEHVPX
tELQV
tVPHEL
tVPLEL
tELEH
PROGRAM
VERIFY
AI01270
Figure 8. Programming Flowchart
VCC = 6.25V, VPP = 12.75V
SET MARGIN MODE
n=0
NO
++n
= 25
YES
E = 50µs Pulse
NO
VERIFY
YES
++ Addr
FAIL
Last NO
Addr
YES
RESET MARGIN MODE
CHECK ALL BYTES
1st: VCC = 5V
2nd: VCC = 2.7V
AI01271C
PRESTO IIB Programming Algorithm
PRESTO IIB Programming Algorithm allows the
whole array to be programmed with a guaranteed
margin, in a typical time of 52.5 seconds. This can
be achieved with STMicroelectronics M27W801
due to several design innovations to improve pro-
gramming efficiency and to provide adequate mar-
gin for reliability. Before starting the programming
the internal MARGIN MODE circuit must be set in
order to guarantee that each cell is programmed
with enough margin. Then a sequence of 50µs
program pulses are applied to each byte until a
correct verify occurs (see Figure 8). No overpro-
gram pulses are applied since the verify in MAR-
GIN MODE at VCC much higher than 3.6V,
provides the necessary margin.
Program Inhibit
Programming of multiple M27W801s in parallel
with different data is also easily accomplished. Ex-
cept for E, all like inputs including GVPP of the par-
allel M27W801 may be common. A TTL low level
pulse applied to a M27W801’s E input, with VPP at
12.75V, will program that M27W801. A high level
E input inhibits the other M27W801s from being
programmed.
Program Verify
A verify (read) should be performed on the pro-
grammed bits to determine that they were correct-
ly programmed. The verify is accomplished with G
at VIL. Data should be verified with tELQV after the
falling edge of E.
9/16
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