M95256-CS3G View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'M95256-CS3G' PDF : 48 Pages View PDF
M95256-DR, M95256, M95256-W, M95256-R
Operating features
4.2
Status Register
Figure 4 shows the position of the Status Register in the control logic of the device. The
Status Register contains a number of status and control bits that can be read or set (as
appropriate) by specific instructions. For a detailed description of the Status Register bits,
see Section 5.3: Read Status Register (RDSR).
4.3
Data protection and protocol control
Non-volatile memory devices can be used in environments that are particularly noisy, and
within applications that could experience problems if memory bytes are corrupted.
Consequently, the device features the following data protection mechanisms:
● Write and Write Status Register instructions are checked that they consist of a number
of clock pulses that is a multiple of eight, before they are accepted for execution.
● All instructions that modify data must be preceded by a Write Enable (WREN)
instruction to set the Write Enable Latch (WEL) bit. This bit is returned to its reset state
by the following events:
– Power-up
– Write Disable (WRDI) instruction completion
– Write Status Register (WRSR) instruction completion
– Write (WRITE) instruction completion
● The Block Protect (BP1, BP0) bits in the Status Register allow part of the memory to be
configured as read-only.
● The Write Protect (W) signal is used to protect the Block Protect (BP1, BP0) bits of the
Status Register.
For any instruction to be accepted, and executed, Chip Select (S) must be driven high after
the rising edge of Serial Clock (C) for the last bit of the instruction, and before the next rising
edge of Serial Clock (C).
Two points need to be noted in the previous sentence:
● The ‘last bit of the instruction’ can be the eighth bit of the instruction code, or the eighth
bit of a data byte, depending on the instruction (except for Read Status Register
(RDSR) and Read (READ) instructions).
● The ‘next rising edge of Serial Clock (C)’ might (or might not) be the next bus
transaction for some other device on the SPI bus.
Table 2. Write-protected block size
Status Register bits
BP1
BP0
Protected block
0
0
none
0
1
Upper quarter
1
0
Upper half
1
1
Whole memory
Protected array addresse
M95256, M95256-W, M95256-R
none
6000h - 7FFFh
4000h - 7FFFh
0000h - 7FFFh
Doc ID 12276 Rev 11
13/48
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