M27C64A Datasheet, PDF (4/12 Pages) STMicroelectronics – 64 Kbit 8Kb x 8 UV EPROM and OTP EPROM

M27C64A
Programming
When delivered (and after each erasure for UV
EPROM), all bits of the M27C64A are in the "1"
state. Data is introduced by selectively program-
ming "0"s into the desired bit locations. Although
only "0"s will be programmed, both "1"s and "0"s
can be present in the data word. The only way to
change a "0" to a "1" is by die exposition to ultra-
violet light (UV EPROM). The M27C64A is in the
programming mode when Vpp input is at 12.5V, E
is at VIL and P is pulsed to VIL. The data to be
programmed is applied to 8 bits in parallel to the
data output pins. The levels required for the ad-
dress and data inputs are TTL. VCC is specified to
be 6V ± 0.25V.
High Speed Programming
The high speed programming algorithm, described
in the flowchart, rapidly programs the M27C64A
using an efficient and reliable method, particularly
suited to the production programming environ-
ment. An individual device will take around 1 minute
to program.
Program Inhibit
Programming of multiple M27C64A in parallel with
different data is also easily accomplished. Except
for E, all like inputs including G of the parallel
M27C64A may be common. A TTL low level pulse
applied to a M27C64A P input, with E low and VPP
at 12.5V, will program that M27C64A. A high level
E input inhibits the other M27C64A from being
programmed.
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 E
and G at VIL, P at VIH, VPP at 12.5V and VCC at 6V.
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 program-
ming the M27C64A. To activate the ES mode, the
programming equipment must force 11.5V to 12.5V
on address line A9 of the M27C64A, with
VPP=VCC=5V. Two identifier bytes may then be
sequenced from the device outputs by toggling
address line A0 from VIL to VIH. All other address
lines must be held at VIL during Electronic Signa-
ture mode.
Byte 0 (A0=VIL) represents the manufacturer code
and byte 1 (A0=VIH) the device identifier code. For
the STMicroelectronics M27C64A, these two iden-
tifier bytes are given in Table 4 and can be read-out
on outputs Q0 to Q7.
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