Datasheet

MCP41XXX/42XXX
DS11195C-page 18  2003 Microchip Technology Inc.
FIGURE 5-1: Timing Diagram for Writing Instructions or Data to a Digital Potentiometer.
FIGURE 5-2: Command Byte Format.
SO
‡
SI
SCK
CS
†
2345678 9101
New Register Data
D7 D6 D5 D4 D3 D2 D1 D0
P1*
P0
11 12 13 14 15 16
X
C1
C0
X
X
X
Channel
Select
Bits
Data Registers are
loaded on rising
edge of CS. Shift
First 16 bits shifted out will always be zeros
Don’t
Care
Bits
Command
Bits
Don’t
Care
Bits
†
There must always be multiples of 16 clocks while CS is low or commands will abort.
‡
The serial data out pin (SO) is only available on the MCP42XXX device.
*
P1 is a ‘don’t care’ bit for the MCP41XXX.
COMMAND Byte Data Byte
X
register is loaded
with zeros at this time.
Data is always latched
in on the rising edge
Data is always clocked out
of the SO pin after the
SO pin will always
drive low when CS
goes high.
of SCK.
falling edge of SCK.
P1* P0 Potentiometer Selections
0 0 Dummy Code: Neither Potentiometer
affected.
0 1 Command executed on
Potentiometer 0.
1 0 Command executed on
Potentiometer 1.
1 1 Command executed on both
Potentiometers.
P0P1*XXXXC1C0
COMMAND BYTE
C1 C0 Command Command Summary
0 0 None No Command will be executed.
0 1 Write Data Write the data contained in Data Byte to the
potentiometer(s) determined by the potenti-
ometer selection bits.
1 0 Shutdown Potentiometer(s) determined by potentiome-
ter selection bits will enter Shutdown Mode.
Data bits for this command are ‘don’t cares’.
1 1 None No Command will be executed.
Command
Selection
Bits
Potentiometer
Selection
Bits