MCP41XXX/42XXX
Data is always latched
Data is always clocked out
of the SO pin after the
falling edge of SCK.
in on the rising edge
of SCK.
Data Registers are
loaded on rising
CS†
edge of CS. Shift
register is loaded
with zeros at this time.
1
2
3
4
5
6
7
8
9
10
11 12 13 14 15 16
SCK
COMMAND Byte
Data Byte
Don’t
Don’t
Channel
Select
Bits
Care
Bits
Command Care
New Register Data
Bits
Bits
X
X
X
C0
X
P1*
P0
D7 D6 D5 D4 D3 D2 D1 D0
C1
SI
SO pin will always
drive low when CS
goes high.
First 16 bits shifted out will always be zeros
X
SO‡
† 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.
FIGURE 5-1:
Timing Diagram for Writing Instructions or Data to a Digital Potentiometer.
COMMAND BYTE
X
X C1 C0 X X P1* P0
Potentiometer
Selection
Bits
Command
Selection
Bits
C1 C0 Command
Command Summary
P1* P0
Potentiometer Selections
0
0
0
1
None
No Command will be executed.
0
0
1
1
0
1
0
1
Dummy Code: Neither Potentiometer
affected.
Command executed on
Potentiometer 0.
Command executed on
Potentiometer 1.
Command executed on both
Potentiometers.
Write Data Write the data contained in Data Byte to the
potentiometer(s) determined by the potenti-
ometer selection bits.
1
1
0
1
Shutdown
Potentiometer(s) determined by potentiome-
ter selection bits will enter Shutdown Mode.
Data bits for this command are ‘don’t cares’.
None
No Command will be executed.
FIGURE 5-2:
Command Byte Format.
DS11195C-page 18
2003 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
