Datasheet

MCP453X/455X/463X/465X
DS22096B-page 60  2008-2013 Microchip Technology Inc.
7.7 Decrement Wiper
Normal and High Voltage
The Decrement Command provides a quick and easy
method to modify the potentiometer’s wiper by -1, with
minimal overhead. The Decrement Command will only
function on the volatile wiper setting memory locations
00h and 01h.
When executing a Decrement Command, the volatile
wiper setting will be altered from n to n-1 for each
Decrement Command received. The value will
decrement down to a minimum of 000h. If multiple Dec-
rement Commands are received after the value has
reached 000h, the value will not be decremented fur-
ther. Table 7-5 shows the Increment Command versus
the current volatile wiper value.
Refer to Figure 7-8 for the Decrement Command
sequence. The sequence is terminated by the Stop
condition. So when executing a continuous command
string, The Increment command can be followed by any
other valid command. this means that writes do not
need to be to the same volatile memory address.
The advantage of using a Decrement Command
instead of a read-modify-write series of commands is
speed and simplicity. The wiper will transition after each
Command Acknowledge when accessing the volatile
wiper registers.
TABLE 7-5: DECREMENT OPERATION VS.
VOLATILE WIPER VALUE
7.7.1 THE HIGH VOLTAGE COMMAND
(HVC) SIGNAL
The High Voltage Command (HVC) signal is
multiplexed with Address 0 (A0) and is used to indicate
that the command, or sequence of commands, are in
the High Voltage mode. An HVC/A0 pin voltage > V
IHH
(~8.5V) puts the MCP45XX/46XX device into the High
Voltage mode.
The HVC pin has an internal resistor connection to the
MCP45XX/46XXs internal V
DD
signal.
FIGURE 7-8: I
2
C Decrement Command Sequence.
Note: Table 7-2 shows the valid addresses for
the Decrement Wiper command. Other
addresses are invalid.
Note: The command sequence can go from an
increment to any other valid command for
the specified address.
Current Wiper
Setting
Wiper (W)
Properties
Decrement
Command
Operates?
7-bit
Pot
8-bit
Pot
3FFh
081h
3FFh
101h
Reserved
(Full-Scale (W = A))
No
080h 100h Full-Scale (W = A) Yes
07Fh
041h
0FFh
081
W = N
040h 080h W = N (Mid-Scale) Yes
03Fh
001h
07Fh
001
W = N
000h 000h Zero Scale (W = B) No
Note: There is a required delay after the HVC pin
is driven to the V
IHH
level to the 1st edge
of the SCL pin.
Control Byte
DECR Command (n-1) DECR Command (n-2)
1010SA2A1A00 1
AD
AD
AD
AD
A0XXA1
AD AD AD AD
0X XAP
(2)
0
1
2
3
4321
Fixed
Address
Variable
Address
Device
Memory
Address
Command
Write bit
Note1: Decrement Command (DECR) only functions when accessing the volatile wiper
registers (AD3:AD0 = 0h and 1h).
2: This command sequence does not need to terminate (using the Stop bit) and can
change to any other desired command sequence (INCR, Read, or Write).