Device description
Figure 5.
Programming flowchart
VCC = 6.25V, VPP = 12.75V
M27W401
n=0
E = 100µs Pulse
NO
++n
= 25
YES
NO
VERIFY
YES
Last
Addr
NO
++ Addr
FAIL
YES
CHECK ALL BYTES
1st: VCC = 5V
2nd: VCC = 2.7V
AI00760C
2.7
Program Inhibit
Programming of multiple M27W401s in parallel with different data is also easily
accomplished. Except for E, all like inputs including G of the parallel M27W401 may be
common. A TTL low level pulse applied to a M27W401's E input, with V
PP
at 12.75V, will
program that M27W401. A high level E input inhibits the other M27W401s 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
, E at V
IH
, V
PP
at 12.75V and
V
CC
at 6.25V.
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 M27W401. To activate
the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of
the M27W401 with V
PP
= V
CC
= 5V. 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
10/23
STMICROELECTRONICS [ STMICROELECTRONICS ]
