MCP98242_09 Datasheet, PDF (32/52 Pages) Microchip Technology – Memory Module Temperature Sensor w/EEPROM for SPD

MCP98242
5.3.3 WRITE PROTECTION
The MCP98242 has a Software Write-Protect (SWP)
feature that allows the lower half array (addresses
00h - 7Fh) to be write-protected or permanently
write-protected (PWP). The write protected area can be
cleared by sending Clear Write Protect (CWP)
command. However, once the PWP is executed the
protected memory can not be cleared. The device will
not respond to the CWP command.
To access write protection, the device address code of
the Address Byte is set to ‘0110’ instead of ‘1010’. The
‘1010’ Address code is used to access the memory
area and the ‘0110’ address code is used to access the
write protection. Once the device is write protected it
will not acknowledge certain commands. Table 5-3
shows the corresponding Address Bytes for the write
protect feature.
TABLE 5-3: WRITE PROTECT DEVICE ADDRESSING
Address Pins
Address Byte
EEPROM
Operation
Slave Address
A2 A1 A0 Address Code
R/W
A2 A1 A0
SWP
WRITE
READ
GND GND V_{HI_A0}
0110
00 1
0
1
CWP
WRITE
READ
GND V_DD V_{HI_A0}
0110
01 1
0
1
PWP (Note)
WRITE
XX
X
0110
XX X
0
READ
1
Note: The Address Pins are ‘X’ or don’t cares. However, the slave address bits need to match the address Pins.
TABLE 5-4: DEVICE RESPONSE WHEN WRITING DATA OR ACCESSING SWP/CWP/PWP
Status
Command
ACK Address ACK Data Byte ACK Write Cycle
Not
Protected
SWP/CWP/PWP
Page/byte write
ACK
X
ACK
X
ACK
Yes
ACK Address ACK
Data
ACK
Yes
Protected
with
SWP
SWP
CWP
PWP
NoACK X NoACK
X
NoACK
No
ACK
X
ACK
X
ACK
Yes
ACK
X
ACK
X
ACK
Yes
Page/byte write lower 128 bytes ACK Address ACK
Data NoACK
No
Permanently
SWP/CWP/PWP
NoACK X NoACK
X
NoACK
No
Protected
Page/byte write lower 128 bytes ACK Address ACK
Data NoACK
No
Note: X is defined as ‘don’t care’.
DS21996C-page 32
© 2009 Microchip Technology Inc.