CAT5259_13 Datasheet, PDF (9/15 Pages) ON Semiconductor – Quad Digital Potentiometer (POT)

I3
(MSB)
CAT5259
Instruction
Opcode
Data Register
Selection
I2
I1
I0
R1
R0
Figure 9. Instruction Byte Format
WCR/Pot Selection
P1
P0
(LSB)
WIPER CONTROL AND DATA REGISTERS
Wiper Control Register (WCR)
The CAT5259 contains four 8-bit Wiper Control
Registers, one for each potentiometer. The Wiper Control
Register output is decoded to select one of 256 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 CAT5259 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 8-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 10 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 13. INSTRUCTION SET (Note: 1/0 = data is one or zero.)
Instruction Set
Instruction
I3 I2 I1 I0 R1 R0 WCR1/P1
Read Wiper Control
Register
1001 0 0
1/0
Write Wiper Control
Register
1010 0 0
1/0
Read Data Register
1 0 1 1 1/0 1/0
1/0
Write Data Register
1 1 0 0 1/0 1/0
1/0
XFR Data Register to
1 1 0 1 1/0 1/0
1/0
Wiper Control Register
XFR Wiper Control
Register to Data
Register
1 1 1 0 1/0 1/0
1/0
Gang XFR Data
Registers to Wiper
Control Registers
0 0 0 1 1/0 1/0
0
Gang XFR Wiper Control 1 0 0 0 1/0 1/0
0
Registers to Data
Register
Increment/Decrement
0010 0 0
1/0
Wiper Control Register
WCR0/P0
1/0
1/0
1/0
1/0
1/0
1/0
0
0
1/0
Operation
Read the contents of the Wiper Control
Register pointed to by P1−P0
Write new value to the Wiper Control Register
pointed to by P1−P0
Read the contents of the Data Register pointed
to by P1−P0 and R1−R0
Write new value to the Data Register pointed to
by P1−P0 and R1−R0
Transfer the contents of the Data Register
pointed to by P1−P0 and R1−R0 to its
associated Wiper Control Register
Transfer the contents of the Wiper Control
Register pointed to by P1−P0 to the Data
Register pointed to by R1−R0
Transfer the contents of the Data Registers
pointed to by R1−R0 of all four pots to their
respective Wiper Control Registers
Transfer the contents of both Wiper Control
Registers to their respective data Registers
pointed to by R1−R0 of all four pots
Enable Increment/decrement of the Control
Latch pointed to by P1−P0
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