Device operation M27W512
10/22
2.6 PRESTO IIB programming algorithm
PRESTO IIB programming algorithm allows the whole array to be programmed with a
guaranteed margin, in a typical time of 6.5 seconds. This can be achieved with
STMicroelectronics M27W512 due to several design innovations described in the M27W512
datasheet to improve programming efficiency and to provide adequate margin 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 100µs
program pulses is applied to each byte until a correct verify occurs (see Figure 3). No
overprogram pulses are applied since the verify in MARGIN MODE at V
CC
much higher than
3.6V, provides the necessary margin.
2.7 Program inhibit
Programming of multiple devices in parallel with different data is also easily accomplished.
Except for E
, all like inputs including GV
PP
of the parallel M27W512 may be common. A TTL
low level pulse applied to a M27W512 E
input, with V
PP
at 12.75V, will program this device.
A high level E
input inhibits the other M27W512 from being programmed.
2.8 Program verify
A verify (read) should be performed on the programmed bits to determine that they were
correctly programmed. The verify is accomplished with G
at V
IL
. Data should be verified with
t
ELQV
after the falling edge of E.
2.9 Electronic signature
The Electronic Signature (ES) mode allows the reading out of a binary code from an
EPROM that will identify its manufacturer and type. This mode is intended for use by
programming equipment to automatically match the device to be programmed with its
corresponding programming algorithm. The ES mode is functional in the 25°C ± 5°C
ambient temperature range that is required when programming the M27W512. To activate
the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of
the M27W512. Two identifier bytes may then be sequenced from the device outputs by
toggling address line A0 from V
IL
to V
IH
. All other address lines must be held at V
IL
during
Electronic Signature mode. Byte 0 (A0 = V
IL
) represents the manufacturer code and byte 1
(A0 = V
IH
) the device identifier code. For the STMicroelectronics M27W512, these two
identifier bytes are given in Tabl e 3 and can be read-out on outputs Q7 to Q0.
Note that the M27W512 and M27C512 have the same identifier byte.
Obsolete Product(s) - Obsolete Product(s)
