MCP4021 datasheet(31/64 Pages) MICROCHIP

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DS21945E-page 31

MCP4021/2/3/4

5.2.2

INCREMENT WITH WRITING WIPER

SETTING TO EEPROM

This mode is achieved by initializing the U/D pin to a

high state (VIH) prior to achieving a low state (VIL) on the

CS pin. Subsequent rising edges of the U/D pin

increment the wiper setting toward terminal A. This is

shown in Figure 5-2.

After the wiper is incremented to the desired position,

the U/D pin should be driven low (VIL). Then when the

CS pin is forced to VIH, the wiper value is written to the

EEPROM. Therefore, if the device voltage is lowered

below the RAM retention voltage of the device, once

the device returns to the operating range, the wiper will

be loaded with this wiper setting (stored in the

EEPROM).

To ensure that “unexpected” transitions on the U/D pin

do not cause the wiper setting to increment, the U/D pin

should be driven low and the CS pin forced to VIH as

soon as possible (within device specifications) after the

last desired increment occurs.

After the CS pin is driven to VIH (from VIL), all other

serial commands are ignored until the EEPROM write

cycle (twc) completes.

FIGURE 5-2:

Increment with Writing Wiper Setting to EEPROM.

Note:

The wiper value will not overflow. That is,

once the wiper value equals 0x3F,

subsequent increment commands are

ignored.

EEPROM

U/D

Wiper

WiperLock™ Technology

WiperLock Technology Enable

WiperLock Technology Disable

X+1

X+2

X+3

X+4

Note: If WiperLock technology enabled, wiper will not move.

VIH

VIL

tWC

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