CAT5259_08 Datasheet, PDF (9/16 Pages) Catalyst Semiconductor – Quad Digitally Programmable Potentiometers (DPP™) with 256 Taps and I²C Interface

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
CAT5259
Register. Any data changes in one of the Data
Registers is a non-volatile operation and will take a
maximum of 10ms.
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
The basic sequence of the three byte instructions is
illustrated in Figure 8. These three-byte instructions
Table 3. Instruction Set
Instruction Set
Instruction
I3 I2 I1 I0 R1 R0 WCR1/P1 WCR0/P0
Operation
Read Wiper Control
Register
1001 0 0
1/0
1/0
Read the contents of the Wiper Control
Register pointed to by P1-P0
Write Wiper Control
Register
1010 0 0
1/0
1/0
Write new value to the Wiper Control
Register pointed to by P1-P0
Read Data Register
1 0 1 1 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
1 1 0 0 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
Wiper Control Register
1
1
0
1 1/0 1/0
1/0
Transfer the contents of the Data Register
1/0 pointed to by P1-P0 and R1-R0 to its
associated Wiper Control Register
XFR Wiper Control
Transfer the contents of the Wiper Control
Register to Data
1 1 1 0 1/0 1/0 1/0
1/0 Register pointed to by P1-P0 to the Data
Register
Register pointed to by R1-R0
Gang XFR Data
Transfer the contents of the Data Registers
Registers to Wiper
0 0 0 1 1/0 1/0
0
0
pointed to by R1-R0 of all four pots to their
Control Registers
respective Wiper Control Registers
Gang XFR Wiper
Transfer the contents of both Wiper Control
Control Registers to 1 0 0 0 1/0 1/0
0
0
Registers to their respective data Registers
Data Register
pointed to by R1-R0 of all four pots
Increment/Decrement
Wiper Control Register
0
0
1
0
0
0
1/0
1/0
Enable Increment/decrement of the Control
Latch pointed to by P1-P0
Note: 1/0 = data is one or zero.
© Catalyst Semiconductor, Inc.
9
Characteristics subject to change without notice
Doc. No. MD-2000 Rev. H