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M29W008AT Datasheet(PDF) 6 Page - STMicroelectronics

Part No. M29W008AT
Description  8 Mbit 1Mb x8, Boot Block Low Voltage Single Supply Flash Memory
Download  30 Pages
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Maker  STMICROELECTRONICS [STMicroelectronics]
Homepage  http://www.st.com
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M29W008AT Datasheet(HTML) 6 Page - STMicroelectronics

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M29W008AT, M29W008AB
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DEVICE OPERATIONS
See Tables 5, 6 and 7.
Read. Read operations are used to output the
contents of the Memory Array, the Electronic Sig-
nature, the Status Register or the Block Protection
Status. Both Chip Enable E and Output Enable G
must be low in order to read the output of the mem-
ory. A new read operation is initiated either on the
falling edge of Chip, Enable E, or on any address
transition with E at VIL.
Write. Write operations are used to give Instruc-
tion Commands to the memory or to latch input
data to be programmed. A write operation is initi-
ated when Chip Enable E is Low and Write Enable
W is Low with Output Enable G High. Addresses
are latched on the falling edge of W or E whichever
occurs last. Commands and Input Data are
latched on the rising edge of W or E whichever oc-
curs first.
Output Disable. The data outputs are high im-
pedance when the Output Enable G is High with
Write Enable W High.
Stand-by. The memory is in stand-by when Chip
Enable E is High and the P/E.C. is idle. The power
consumption is reduced to the stand-by level and
the outputs are high impedance, independent of
the Output Enable G or Write Enable W inputs.
Automatic Stand-by. After 150ns of bus inactivi-
ty (no address transition, E = VIL) and when CMOS
levels are driving the addresses, the chip automat-
ically enters a pseudo-stand-by mode where con-
sumption is reduced to the CMOS stand-by value,
while outputs still drive the bus (if G = VIL).
Electronic Signature. Two codes identifying the
manufacturer and the device can be read from the
memory. The manufacturer’s code for STMicro-
electronics is 20h, the device code is D2h for the
M29W008AT
(Top
Boot)
and
DCh
for
the
M29W008AB (Bottom Boot). These codes allow
programming equipment or applications to auto-
matically match their interface to the characteris-
tics of the M29W008A. The Electronic Signature is
output by a Read operation when the voltage ap-
plied to A9 is at VID and address inputs A1 is Low.
The manufacturer code is output when the Ad-
dress input A0 is Low and the device code when
this input is High. Other Address inputs are ig-
nored. The Electronic Signature can also be read,
without raising A9 to VID, by giving the memory the
Instruction AS.
Block Protection. Each block can be separately
protected against Program or Erase on program-
ming equipment. Block protection provides addi-
tional data security, as it disables all program or
erase operations. This mode is activated when
both A9 and G are raised to VID and an address in
the block is applied on A13-A19. Block protection
is initiated on the edge of W falling to VIL. Then af-
ter a delay of 100µs, the edge of W rising to VIH
ends the protection operations. Block protection
verify is achieved by bringing G, E, A0 and A6 to
VIL and A1 to VIH, while W is at VIH and A9 at VID.
Under these conditions, reading the data output
will yield 01h if the block defined by the inputs on
A13-A19 is protected. Any attempt to program or
erase a protected block will be ignored by the de-
vice.
Block Temporary Unprotection. Any previously
protected block can be temporarily unprotected in
order to change stored data. The temporary un-
protection mode is activated by bringing RP to VID.
During the temporary unprotection mode the pre-
viously protected blocks are unprotected. A block
can be selected and data can be modified by exe-
cuting the Erase or Program instruction with the
RP signal held at VID. When RP is returned to VIH,
all the previously protected blocks are again pro-
tected.
Block Unprotection. All protected blocks can be
unprotected on programming equipment to allow
updating of bit contents. All blocks must first be
protected before the unprotection operation. Block
unprotection is activated when A9, G and E are at
VID and A12, A15 at VIH. Unprotection is initiated
by the edge of W falling to VIL. After a delay of
10ms, the unprotection operation will end. Unpro-
tection verify is achieved by bringing G and E to
VIL while A0 is at VIL, A6 and A1 are at VIH and A9
remains at VID. In these conditions, reading the
output data will yield 00h if the block defined by the
inputs A13-A19 has been successfully unprotect-
ed. Each block must be separately verified by giv-
ing its address in order to ensure that it has been
unprotected.


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