CAT5419WI-25 Datasheet, PDF (9/16 Pages) ON Semiconductor – Dual Digitally Programmable Potentiometers with 64 Taps and 2-wire Interface

WIPER CONTROL AND DATA REGISTERS
Wiper Control Register (WCR)
The CAT5419 contains two 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 CAT5419 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
CAT5419
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 5ms.
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 3. Instruction Set
Instruction Set
Instruction
I3 I2 I1 I0 R1 R0
0
Read Wiper Control
1001 0 0
0
Register
Write Wiper Control
1010 0 0
0
Register
Read Data Register
1 0 1 1 1/0 1/0
0
Write Data Register
1 1 0 0 1/0 1/0
0
XFR Data Register to
1 1 0 1 1/0 1/0
0
Wiper Control Register
XFR Wiper Control
1 1 1 0 1/0 1/0
0
Register to Data
Register
Gang XFR Data
Registers to Wiper
Control Registers
0 0 0 1 1/0 1/0
0
Gang XFR Wiper
1 0 0 0 1/0 1/0
0
Control Registers to
Data Register
Increment/Decrement
0010 0 0
0
Wiper Control Register
Note: 1/0 = data is one or zero
WCR0/ P0 Operation
1/0
Read the contents of the Wiper Control
Register pointed to by P0
1/0
Write new value to the Wiper Control
Register pointed to by P0
1/0
Read the contents of the Data Register
pointed to by P0 and R1-R0
1/0
Write new value to the Data Register
pointed to by P0 and R1-R0
1/0
Transfer the contents of the Data
Register pointed to by P0 and R1-R0 to
its associated Wiper Control Register
1/0
Transfer the contents of the Wiper
Control Register pointed to by P0 to the
Data Register pointed to by R1-R0
0
Transfer the contents of the Data
Registers pointed to by R1-R0 of both
pots to their respective Wiper Control
Registers
0
Transfer the contents of both Wiper
Control Registers to their respective data
Registers pointed to by R1-R0 of both
four pots
1/0
Enable Increment/decrement of the
Control Latch pointed to by P0
2008 SCILLC. All rights reserved.
9
Characteristics subject to change without notice
Doc. No. MD-2115 Rev. I