CAT5241_13 Datasheet, PDF (10/16 Pages) ON Semiconductor – Quad Digital Potentiometer (POT)

CAT5241
Wiper Control and Data Registers
Wiper Control Register (WCR)
The CAT5241 contains four 6-bit Wiper Control
Registers, one for each potentiometer. The Wiper Control
Register output is decoded to select one of 64 switches along
its resistor array. The contents of the WCR can be altered in
four ways: it may be written by the host via Write Wiper
Control Register instruction; it may be written by
transferring the contents of one of four associated Data
Registers via the XFR Data Register instruction, it can be
modified one step at a time by the Increment/decrement
instruction (see Instruction section for more details).
Finally, it is loaded with the content of its data register zero
(DR0) upon power-up.
The Wiper Control Register is a volatile register that loses
its contents when the CAT5241 is powered-down. Although
the register is automatically loaded with the value in DR0
upon power-up, this may be different from the value present
at power-down.
Data Registers (DR)
Each potentiometer has four 6-bit non-volatile Data
Registers. These can be read or written directly by the host.
Data can also be transferred between any of the four Data
Registers and the associated Wiper Control Register. Any
data changes in one of the Data Registers is a non-volatile
operation and will take a maximum of 5 ms.
If the application does not require storage of multiple
settings for the potentiometer, the Data Registers can be used
as standard memory locations for system parameters or user
preference data.
Instructions
Four of the nine instructions are three bytes in length.
These instructions are:
 Read Wiper Control Register – read the current wiper
position of the selected potentiometer in the WCR
 Write Wiper Control Register – change current wiper
position in the WCR of the selected potentiometer
 Read Data Register – read the contents of the selected
Data Register
 Write Data Register – write a new value to the
selected Data Register.
Table 12. INSTRUCTION SET (Note: 1/0 = data is one or zero)
Instruction Set
Instruction
Read Wiper Control
Register
I3 I2 I1 I0 WCR1/P1 WCR0/P0 R1 R0
Operations
1001
1/0
1/0
0 0 Read the contents of the Wiper
Control Register pointed to by P1−P0
Write Wiper Control
1010
1/0
Register
1/0
0 0 Write new value to the Wiper Control
Register pointed to by P1−P0
Read Data Register
1011
1/0
1/0
1/0 1/0 Read the contents of the Data
Register pointed to by P1−P0 and
R1−R0
Write Data Register
1100
1/0
1/0
1/0 1/0 Write new value to the Data Register
pointed to by P1−P0 and R1−R0
XFR Data Register to
1101
1/0
Wiper Control Register
1/0
1/0 1/0 Transfer the contents of the Data
Register pointed to by P1−P0 and
R1−R0 to its associated Wiper Control
Register
XFR Wiper Control
1110
1/0
Register to Data
Register
1/0
1/0 1/0 Transfer the contents of the Wiper
Control Register pointed to by P1−P0
to the Data Register pointed to by
R1−R0
Global XFR Data
0001
0
Registers to Wiper
Control Registers
0
1/0 1/0 Transfer the contents of the Data
Registers pointed to by R1−R0 of all
four pots to their respective Wiper
Control Registers
Global XFR Wiper
1000
0
Control Registers to
Data Register
0
1/0 1/0 Transfer the contents of both Wiper
Control Registers to their respective
data Registers pointed to by R1−R0 of
all four pots
Increment/Decrement
00
1
0
1/0
Wiper Control Register
1/0
0 0 Enable Increment/decrement of the
Control Latch pointed to by P1−P0
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