Memory Blocks
The memory blocks of the M29W040 are shown in
Figure 3. The memory array is divided in 8 uniform
blocks of 64 Kbytes. Each block can be erased
separately or any combination of blocks can be
erased simultaneously. The Block Erase operation
is managed automatically by the P/E.C. The opera-
tion can be suspended in order to read from any
other block, and then resumed.
Block Protection prov ides a dditional data security.
Each uniform block can be separately protected or
unprotected against Program or Erase. Bringing A9
and G to VID initiates protection, while bringing A9,
G and E to VID cancels the protection. The block
affected during protection is addressed by the in-
puts on A16, A17, and A18. Unprotect operation
affects all blocks.
Operations
Operations are defined as specific bus cycles and
signals which allow Memory Read, Command
Write, Output Dis able, Standby, Read Status Bits,
Block Protect/Unprotect, Block Protection Check
and Electronic Signature Read. They are shown in
Tables 3, 4, 5.
Read. Read operations are used to output the
contents of the Memory Array, the Status Register
or the Electronic Signature. Both Chip Enable E
and Output Enable G must be low in order to read
the output of the memory. The Chip Enable input
also provides power control and should be used for
device selection. Output Enable should be used to
gate data onto the output independent of the device
selection. The dat a r ead depends on the previous
command written to the memory (see instructions
RST and RSIG, and Status Bits).
Write. Write operations are used to give Instruction
Commands to the memory or to latch input data to
be programmed. A write operation is initiated 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 occurs first.
Output Disab le. The dat a outputs are high imped-
ance when the Output Enable G is High with W r ite
Enable W High.
Standby. The memory is in standby when Chip
Enable E is High and Program/Erase Controller
P/E.C. is Idle. The power c ons umpt ion is r educ ed
to the standby level and the outputs are high im-
pedance, independent of the Output Enable G or
Write Enable W inputs.
Autom a tic Sta ndby. After 150ns of inactivity and
when CMOS levels are driving the addr esses, t he
chip automat ically ent ers a pseudo s tandby m ode
where consumption is reduced to the CMOS
standby value, while outputs are still driving the
bus.
Power Down. When the PD command is written
to the P/E.C. the memory enters a power down
status where the power consumption is reduced to
ICC6 (typically less than 1.0µA).
Electronic Signature. Two codes identifying t he
manufacturer and the device can be read from the
memory, the manufacturer’s code for STMicroelec-
tronics is 20h, and the device code is E3h for the
M29W040. These codes allow programming
equipment or applications to automat ic ally m atch
their interface to the characteristics of the particular
manufacturer’s product. The Electronic S ignature
is output by a Read operation when the voltage
applied to A9 is at VID and addr ess inputs A1 and
A6 are at Low. The manufacturer code is output
when the Address input A0 is Low and the device
code when this input is High. Other Address inputs
are ignored. The codes are output on DQ0-DQ7.
This is shown in Table 4.
The Electronic Signature can also be read, without
raising A9 to VID by giving the memory the instruc-
tion RSIG (see below).
6/31
M29W040