Datasheet

MCP9843/98243
DS22153C-page 38 © 2009 Microchip Technology Inc.
5.3.3.1 Software Write Protect (SWP)
The SWP feature is invoked by writing to the write-
protect register. This is done by sending an Address
Byte similar to a normal Write command. Figure 5-17
shows the timing diagram. SWP can be cleared using
the CWP command. See Section 5.3.3.2 “Clear Write
Protect (CWP)”
The Slave Address bits need to correspond to the
address pin logic configuration. For SWP, a high
voltage V
HV
needs to be applied to the A0 pin and the
corresponding slave address needs to be set to ‘1’, as
shown in Table 5-3. Both A2 and A1 pins are grounded
and the corresponding slave address bits are set to ‘0’.
The device response in this mode is shown in Tabl e 5 -
4 and Tabl e 5 - 5.
FIGURE 5-15: Timing Diagram for Setting Software Write Protect (See Section 4.0 “Serial
Communication”).
5.3.3.2 Clear Write Protect (CWP)
The CWP feature is invoked by writing to the clear
write-protect register. This is done by sending an
Address Byte similar to a normal Write command.
Figure 5-17 shows the timing diagram. CWP clears
SWP only. PWP can not be cleared using this
command.
The Slave Address bits need to correspond to the
address pin logic configuration. For CWP, a high
voltage V
HV
needs to be applied to the A0 pin and the
corresponding slave address needs to be set to ‘1’.
The A1 pin is set to V
DD
and the corresponding slave
address bit is set to ‘1’. And A2 pins is set to ground
and the corresponding slave address bits are set to ‘0’.
Table 5-3 shows the bit configuration. The device
response in this mode is shown in Tab l e 5 -4 and
Table 5-5.
FIGURE 5-16: Timing Diagram for Setting Clear Write Protect (See Section 4.0 “Serial
Communication”).
SDA
A
C
K
0110
A
C
K
S
12345678 12345678
SCL
Address Byte
W
MCP98243
MCP98243
A
C
K
P
12345678
Data
Word Address
MCP98243
XXXXX
XXX XXXXX
XXX
001
Note: Apply V
HV
at A0 pin and connect GND to A1 and A2 pins to initiate SWP cycle.
SDA
A
C
K
0110
A
C
K
S
12345678 12345678
SCL
Address Byte
W
MCP98243
MCP98243
A
C
K
P
12345678
Data
Word Address
MCP98243
XXXXX
XXX XXXXX
XXX
011
Note: Apply V
HV
at A0 pin, apply V
DD
at A1 pin, connect A2 pin to GND to initiate CWP cycle.