MCP4021 datasheet(32/64 Pages) MICROCHIP

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MCP4021/2/3/4

DS21945E-page 32

5.2.3

DECREMENT WITHOUT WRITING

WIPER SETTING TO EEPROM

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

state (VIL) prior to achieving a low state (VIL) on the CS

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

decrement the wiper setting toward terminal B. This is

shown in Figure 5-3.

After the wiper is decremented to the desired position,

the U/D pin should be forced low (VIL) and the CS pin

should be forced to VIH. This will ensure that

“unexpected” transitions on the U/D pin do not cause

the wiper setting to decrement. Driving the CS pin to

VIH should occur as soon as possible (within device

specifications) after the last desired increment occurs.

The EEPROM value has not been updated to this new

wiper value, so, 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 the wiper setting in the EEPROM.

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

serial command may immediately be entered, since an

EEPROM write cycle (tWC) is not started.

FIGURE 5-3:

Decrement without Writing Wiper Setting to EEPROM.

Note:

The wiper value will not underflow. That is,

once the wiper value equals 0x00,

subsequent decrement 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 change.

VIH

VIL

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