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AN1436 APPLICATION NOTE
Changing from the ST95010/ST95020 to the M95010/M95020 In Your Application Using a Simple Recognition Method
Customers who upgrade from the ST95010, or ST95020, to the M95010, or M95020, in their production could be interested in the algorithm described in this document. It is a simple way for the application automatically to identify the memory parts mounted on board. INSTRUCTION CODE FORMAT There are only two differences between the ST95010 and the M95010, and between the ST95020 and the M95020:
s s
Performance (the M95 offers a significant performance improvement over the ST95 family) Instruction format
ST95010 and ST95020 instructions have the following format (where I2, I1, and I0 are instruction bits, as documented in the data sheet):
0 0 0 0 0 I2 I1 I0
while M95010 and M95020 instructions have the following format (where I2, I1, and I0 are instruction bits, as documented in the data sheet, and X represents a Don't Care bit):
0 0 0 0 X I2 I1 I0
SOFTWARE RECOGNITION ALGORITHM This difference can be used by the application software to differentiate between the two types of memory device (between the ST95010 and the M95010, and between the ST95020 and the M95020). Table 1 compares the instruction formats of these devices. Table 1. Differences between the Instruction Formats
Instruction Format Instruction Description ST95010 ST95020 0000 0110 0000 0100 0000 0101 0000 0001 0000 0011 0000 0010 M95010 M95020 0000 X110 0000 X100 0000 X101 0000 X001 0000 X011 0000 X010
WREN WRDI RDSR WRSR READ WRITE
Set Write Enable Latch Reset Write Enable Latch Read Status Register Write Status Register Read Data from Memory Area Write Data to Memory Array
As shown in Table 1, "0000 1101" is a valid Write Enable (WREN) instruction for the M95010 and M95020, but not for the ST95010 or ST95020.
June 2001
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AN1436 - APPLICATION NOTE
The Write Enable Latch (WEL) bit, in the status register of the memory device, must be set to 1 before a Write Data Bytes (WRITE) is accepted by the memory. The Write Enable (WREN) instruction is used to set this bit. 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. This algorithm only activates the internal logic of the memory device, and is therefore fast to execute, and does not have any significant impact on the performance of the application. After Power-up, the following algorithm is executed: - The Bus Master sends a Write Enable (WREN) instruction (0000 1110) to the memory - The Bus Master sends a Read Status Register (RDSR) instruction (0000 0101) to the memory, and stores the value of the Write Enable Latch (WEL) bit in a variable called WEL1 - The Bus Master sends a modified Write Disable (WRDI) instruction (0000 1100) to the memory - The Bus Master sends a Read Status Register (RDSR) instruction (0000 0101) to the memory, and stores the value of the Write Enable Latch (WEL) bit in a variable called WEL2. - If (WEL1,WEL2)=(1,0) Then the device is an M95010/20, Else the device is an ST95010/20 - The Bus Master sends a Write Disable (WRDI) instruction (0000 0100) to protect the application from data corruption
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AN1436 - APPLICATION NOTE
If you have any questions or suggestions concerning the matters raised in this document, please send them to the following electronic mail addresses:
apps.eeprom@st.com ask.memory@st.com
(for application support) (for general enquiries)
Please remember to include your name, company, location, telephone number and fax number.
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is registered trademark of STMicroelectronics All other names are the property of their respective owners (c) 2001 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. www.st.com
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