Datasheet

MCP4021/2/3/4
DS21945E-page 26 © 2006 Microchip Technology Inc.
3.6 Chip Select (CS)
The CS pin is the chip select input. Forcing the CS pin
to V
IL
enables the serial commands. These commands
can increment and decrement the wiper. Depending on
the command, the wiper may (or may not) be saved to
non-volatile memeory (EEPROM). Forcing the CS
pin
to V
IHH
enables the high-voltage serial commands.
These commands can increment and decrement the
wiper and enable or disable the WiperLock technology.
The wiper is saved to non-volatile memory (EEPROM).
The CS
pin has an internal pull-up resistor. The resistor
will become “disabled” when the voltage on the CS
pin
is below the V
IH
level. This means that when the CS pin
is “floating”, the CS pin will be pulled to the V
IH
level
(serial communication (the U/D
pin) is ignored). And
when the CS pin is driven low (V
IL
), the resistance
becomes very large to reduce the device current
consumption when serial commands are occurring.
See Figure 2-4 for additional information.
3.7 Increment/Decrement (U/D)
The U/D pin input is used to increment or decrement
the wiper on the digital potentiometer. An increment
moves the wiper one step toward terminal A, while a
decrement moves the wiper one step toward
terminal B.