Datasheet

MCP4011/2/3/4
DS21978C-page 32 © 2006 Microchip Technology Inc.
5.2.3 DECREMENT
This mode is achieved by initializing the U/D pin to a low
state (V
IL
) prior to achieving a low state (V
IL
) 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 (V
IL
) and the CS pin
should be forced to V
IH
. This will ensure that
“unexpected” transitions on the U/D pin do not cause
the wiper setting to decrement. Driving the CS pin to
V
IH
should occur as soon as possible (within device
specifications) after the last desired increment occurs.
When the device voltage falls below the RAM retention
voltage of the device, the wiper state may be corrupted.
When the device returns to the operating range, the
wiper will be loaded with the default POR wiper setting.
After the CS
pin is driven to V
IH
(from V
IL
), any other
serial command may immediately be entered.
FIGURE 5-3: Decrement.
Note: The wiper value will not underflow. That is,
once the wiper value equals 0x00,
subsequent decrement commands are
ignored.
U/D
CS
Wiper
1 2 3 4
X-1XX-2X-3X-4
V
IH
V
IH
5
6
V
IL
V
IL
V
IL