Datasheet

MCP4021/2/3/4
DS21945E-page 38 © 2006 Microchip Technology Inc.
5.2.9 HIGH-VOLTAGE DECREMENT AND
ENABLE WiperLock TECHNOLOGY
This mode is achieved by initializing the U/D pin to the
low state (V
IL
) prior to driving the CS pin to V
IHH
.
Subsequent rising edges of the U/D pin decrement the
wiper setting toward terminal B. Set the U/D pin to a
high state (V
IH
) prior to forcing the CS pin to V
IH
. This
begins a write cycle and enables the WiperLock
Technology feature (See Figure 5-9).
After the CS
pin is driven to V
IH
(from V
IHH
), all other
serial commands are ignored until the EEPROM write
cycle (t
WC
) completes.
FIGURE 5-9: High-Voltage Decrement and Enable WiperLock™ Technology.
Note: The wiper value will not underflow. That is,
once the wiper value equals 0x00,
subsequent decrement commands are
ignored.
EEPROM
U/D
CS
Wiper
1 2 3 4
WiperLock™ Technology
WiperLock Technology Enable
WiperLock Technology Disable
XXXXX
X-4
X-1
X
X-2 X-3 X-4
V
IHH
V
DD
V
IH
V
IH
5
6
V
IH
V
IL
t
WC