M29W400DT, M29W400DB
Bus operations
3.6
Special bus operations
Additional bus operations can be performed to read the electronic signature and also to
apply and remove block protection. These bus operations are intended for use by
programming equipment and are not usually used in applications. They require V
ID
to be
applied to some pins.
3.7
Electronic signature
The memory has two codes, the manufacturer code and the device code, that can be read
to identify the memory. These codes can be read by applying the signals listed in
and
Bus operations.
3.8
Block protection and blocks unprotection
Each block can be separately protected against accidental Program or Erase. Protected
blocks can be unprotected to allow data to be changed.
There are two methods available for protecting and unprotecting the blocks, one for use on
programming equipment and the other for in-system use. Block Protect and Chip Unprotect
operations are described in
Table 2.
Bus operations, BYTE = V
IL(1)
E
V
IL
V
IL
X
V
IH
V
IL
G
V
IL
V
IH
V
IH
X
V
IL
W
V
IH
V
IL
V
IH
X
V
IH
Address inputs
DQ15A–1, A0-A17
Cell address
Command address
X
X
A0 = V
IL
, A1 = V
IL
,
A9 = V
ID
,
others V
IL
or V
IH
A0 = V
IH
, A1 = V
IL
,
A9 = V
ID
,
others V
IL
or V
IH
Data inputs/outputs
DQ14-DQ8
Hi-Z
Hi-Z
Hi-Z
Hi-Z
Hi-Z
DQ7-DQ0
Data output
Data input
Hi-Z
Hi-Z
20h
EEh
(M29W400DT)
EFh
(M29W400DB)
Operation
Bus Read
Bus Write
Output Disable
Standby
Read
manufacturer code
Read device code
V
IL
V
IL
V
IH
Hi-Z
1. X = V
IL
or V
IH
.
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NUMONYX [ NUMONYX B.V ]
