Datasheet

© 2006 Microchip Technology Inc. DS21978C-page 29
MCP4011/2/3/4
5.0 SERIAL INTERFACE
5.1 Overview
The MCP4011/2/3/4 utilizes a simple 2-wire interface to
increment or decrement the digital potentiometer’s
wiper terminal (W). This interface uses the CS and U/D
pins. The CS pin is the Chip Select input, while the U/D
pin is the Up/Down input.
The Increment/Decrement protocol enables the device
to move one step at a time through the range of
possible resistance values. The wiper value is
initialized with the “default” value upon power-up.
A wiper value of 00h connects the wiper to terminal B.
A wiper value of 3Fh connects the wiper to terminal A.
Increment commands move the wiper toward terminal
A, but will not increment to a value greater than 3Fh.
Decrement commands move the wiper toward terminal
B, but will not decrement below 00h.
Refer to Section 1.0 “Electrical Characteristics”,
AC/DC Electrical Characteristics table for detailed input
threshold and timing specifications.
Communication is unidirectional. Therefore, the value
of the current wiper setting cannot be read out of the
MCP401X device.
5.2 Serial Commands
The MCP401X devices support eight serial commands.
Six of these commands are for support and to ease
migration with the MCP402X family of devices. The
commands can be grouped into the following types:
• Serial Commands
• High-voltage Serial Commands
All the commands are shown in Table 5-1.
The command type is determined by the voltage level
the CS
pin is driven to. The initial state that the CS pin
must be driven is V
IH
. From V
IH
, the two levels that the
CS pin can be driven are:
•V
IL
•V
IHH
If the CS
pin is driven from V
IH
to V
IL
, a serial
command is selected. If the CS pin is driven from V
IH
to
V
IHH
, a high-voltage serial command is selected.
Support of the high-voltage serial commands is for
compatiblity with the MCP402X devices.
TABLE 5-1: COMMANDS
Command Name
High Voltage
on CS
pin?
Increment —
Increment (for MCP402X Compatibility) —
Decrement —
Decrement (for MCP402X Compatibility) —
High-Voltage Increment 1 (for MCP402X Compatibility) Yes
High-Voltage Increment 2 (for MCP402X Compatibility) Yes
High-Voltage Decrement 1 (for MCP402X Compatibility) Yes
High-Voltage Decrement 2 (for MCP402X Compatibility) Yes