MCP4432 datasheet(64/94 Pages) MICROCHIP

64 / 94 page

MCP443X/5X

DS22267A-page 64

 2010 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 000h min. If multiple Decrement

Commands are received after the value has reached

000h, the value will not be decremented further.

Table 7-5 shows the Increment Command versus the

current volatile wiper value.

The Decrement Command will most commonly be

performed on the Volatile Wiper locations until a

desired condition is met. The MCP44XX is responsible

for generating the A bits.

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. Signals > VIHH (~8.5V) on the

HVC/A0 pin puts MCP44XX devices into High Voltage

mode.

The HVC pin has an internal resistor connection to the

MCP44XX’s internal VDD signal.

FIGURE 7-8:

I2C Decrement Command Sequence.

Note:

Table 7-5 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))

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

Zero Scale (W = B) No

Note:

There is a required delay after the HVC pin

is driven to the VIHH level to the 1st edge

of the SCL pin.

Control Byte

DECR Command (n-1)

DECR Command (n-2)

01 0

S1 A1 A0 0

AD AD AD AD

A0 X X A

AD AD AD AD

0X X A P (2)

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 = 00h, 01h, 06h, and 07h).

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).

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