M29W400DT Datasheet, PDF (17/48 Pages) STMicroelectronics – 4 Mbit (512Kb x8 or 256Kb x16, Boot Block) 3V Supply Flash Memory

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 Table 2
and Table 3, 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 Appendix B: Block protection.
Table 2. Bus operations, BYTE = V_IL(1)
Operation
E
G
W
Address inputs
DQ15A–1, A0-A17
Bus Read
V_IL
V_IL
V_IH Cell address
Bus Write
V_IL
V_IH
V_IL Command address
Output Disable
X
V_IH
V_IH X
Standby
V_IH
X
XX
Read
manufacturer code
V_IL
V_IL
A0 = V_IL, A1 = V_IL,
V_IH A9 = V_ID,
others V_IL or V_IH
A0 = V_IH, A1 = V_IL,
Read device code V_IL
V_IL
V_IH A9 = V_ID,
others V_IL or V_IH
1. X = V_IL or V_IH.
Data inputs/outputs
DQ14-DQ8
Hi-Z
Hi-Z
Hi-Z
Hi-Z
DQ7-DQ0
Data output
Data input
Hi-Z
Hi-Z
Hi-Z
20h
EEh
(M29W400DT)
Hi-Z
EFh
(M29W400DB)
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