MCP98243 datasheet(37/62 Pages) MICROCHIP

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DS22153C-page 37

MCP9843/98243

5.3.3

WRITE PROTECTION

The MCP98243 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 (NOTE 1)

EEPROM

Operation

Address Pins

Address Byte

Address Code

Slave Address

R/W

SWP

WRITE

GND GND

VHV

0110

READ

CWP

WRITE

GND VDD

VHV

0110

READ

PWP (Note)

WRITE

0110

READ

Note 1: The Address Pins are ‘X’ or don’t cares. However, the slave address bits need to match the address pins.

For VHV voltage levels, refer to Figure 2-13.

TABLE 5-4:

DEVICE RESPONSE WHEN WRITING DATA OR ACCESSING SWP/CWP/PWP

(NOTE 1)

Status

Command

ACK

Address

ACK

Data Byte

ACK

Write Cycle

Not

Protected

SWP/CWP/PWP

ACK

Yes

Page/byte write

ACK

Address

ACK

Data

ACK

Yes

Protected

with

SWP

NoACK

CWP

ACK

Yes

PWP

ACK

Yes

Page/byte write lower 128 bytes

ACK

Address

ACK

Data

NoACK

Permanently

Protected

SWP/CWP/PWP

NoACK

Page/byte write lower 128 bytes

ACK

Address

ACK

Data

NoACK

Note 1: X is defined as ‘don’t care’.

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