AN1116 ST Microelectronics, AN1116 Datasheet - Page 3

• Manufacturer Part Number: AN1116
• Description: CHANGING FROM THE ST95P08 TO THE M95080 IN YOUR APPLICATION USING A SIMPLE SOFTWARE RECOGNITION METHOD
• Manufacturer: ST Microelectronics

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(where X
others).
SOFTWARE RECOGNITION ALGORITHM
This last difference can be used by the application software to differentiate between the two types of mem-
ory device. (For a further summary, please see the comparison of the instruction formats of the two devic-
es, in Table 3).
The WREN instruction is used, prior to any write attempt to the memory, to set an internal logical bit of the
status register which has to be set to 1 to try a write access to the memory.
As described above in the “instruction format“ section, 0001 1101 is a valid WREN instruction code for the
ST95P08, and is not a valid WREN instruction for the M95080.
The following algorithm is short, and easy to insert in the MCU code. It is also safe to use, inasmuch that
it does not attempt to write to any non volatile bits.
– Master sends the WREN instruction “0001 1110“ to the memory (note that b3 and b4 are “1”).
– Master sends the RDSR instruction “0000 0101“ to the memory (note that b3 and b4 are “0” to avoid
– Master sends the WRDI instruction “0001 1100“ to the memory (note that b3 and b4 are “1”).
– Master sends the RDSR instruction “0000 0101“ to the memory (again, b3 and b4 are “0” to avoid the
– If (WEL1,WEL2)= (1,0)
Table 3. Differences Between the ST95P08 and the M95080 Instruction Formats
Notes: 1. A = 1 indicates that the upper page is selected; A = 0 indicates that the lower page is selected
Instruction
the High-Z state on the Q-bus during WEL bit read) and stores the value of the WEL bit in a variable
that we will refer to as WEL1.
High-Z state on the Q-bus during WEL bit read) and stores the value of the WEL bit in a variable that
we will refer to as WEL2.
then the EEPROM device is a ST95P08
else the EEPROM device is an M95080
WRITE
WREN
WRSR
RDSR
READ
WRDI
2. X = Don’t Care
2
and X
1
Set Write Enable Latch
Reset Write Enable Latch
Read Status Register
Write Status Register
Read Data from Memory Array
Write Data to Memory Array
are respectively A9 and A8 for Read and Write operations, and are Don’t Care bits for
Description
000X X110
000X X100
000X X101
000X X001
000A A011
000A A010
ST95P08
AN1116 - APPLICATION NOTE
Instruction Format
0000 0110
0000 0100
0000 0101
0000 0001
0000 0011
0000 0010
M95080
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