Datasheet

MCP4021/2/3/4
DS21945E-page 40 © 2006 Microchip Technology Inc.
5.2.11 WRITE WIPER SETTING TO
EEPROM AND ENABLE WiperLock
TECHNOLOGY
This mode is achieved by initializing the U/D and CS
pins to a high state (V
IH
) prior to the CS pin being driven
to V
IHH
(from V
IH
). Set the U/D pin to a low state (V
IL
)
prior to forcing the CS pin to V
IH
(from V
IHH
). This
begins a write cycle and enables the WiperLock
Technology feature (See Figure 5-11).
To ensure that “unexpected” transitions on the U/D
pin
do not cause the wiper setting to increment, force the
CS pin to V
IH
as soon as possible (within device
specifications) after the U/D
pin is forced to V
IL
.
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 5-11: Write Wiper Setting to EEPROM and Enable WiperLock™ Technology.
EEPROM
U/D
CS
Wiper
WiperLock™ Technology
X+4
X
X+4
WiperLock Technology Enable
WiperLock Technology Disable
V
IHH
V
IH
V
IH
V
IH
V
IL
t
WC