CAT5411WI-25 Datasheet, PDF (9/16 Pages) ON Semiconductor – Dual Digitally Programmable Potentiometers with 64 Taps and SPI Interface

CAT5411
WIPER CONTROL AND DATA REGISTERS
Wiper Control Register (WCR)
The CAT5411 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 CAT5411 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 5ms.
Write in Process
The contents of the Data Registers are saved to
nonvolatile memory when the ^{¯C¯S¯} input goes HIGH
after a write sequence is received. The status of the
internal write cycle can be monitored by issuing a
Read Status command to read the Write in Process
(WIP) bit.
INSTRUCTIONS
Four of the ten 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
— Read Status – Read the status of the WIP bit
which when set to "1" signifies a write cycle is in
progress.
Table 3. Instruction Set
Note: 1/0 = data is one or zero
Instruction Set
Instruction
I3 I2 I1 I0 R1 R0 0 WCR₀/ P0 ^Operations
Read Wiper Control Register 1 0 0 1 0 0 0
1/0
Read the contents of the Wiper Control Register
pointed to by P0
Write Wiper Control Register 1 0 1 0 0 0 0
1/0
Write new value to the Wiper Control Register
pointed to by P0
Read Data Register
1 0 1 1 1/0 1/0 0
1/0
Read the contents of the Data Register pointed to by
P0 and R1-R0
Write Data Register
1 1 0 0 1/0 1/0 0
1/0
Write new value to the Data Register pointed to by
P0 and R1-R0
XFR Data Register to Wiper
Control Register
1
1
0
1 1/0 1/0
0
Transfer the contents of the Data Register pointed to
1/0 by P0 and R1-R0 to its associated Wiper Control
Register
XFR Wiper Control Register
to Data Register
1
1
1
0 1/0 1/0
0
Transfer the contents of the Wiper Control Register
1/0 pointed to by P0 to the Data Register pointed to by
R1-R0
Global XFR Data Registers
to Wiper Control Registers
0 0 0 1 1/0 1/0 0
Transfer the contents of the Data Registers pointed to
0
by R1-R0 of all four pots to their respective Wiper
Control Registers
Global XFR Wiper Control
Registers to Data Register
1 0 0 0 1/0 1/0 0
Increment/Decrement Wiper
Control Register
0
0
1
0
0
0
0
Transfer the contents of both Wiper Control Registers
0
to their respective data Registers pointed to by
R1-R0 of all four pots
1/0
Enable Increment/decrement of the Control Latch
pointed to by P0
Read Status
0101 0 0 0
1
Read WIP bit to check internal write cycle status
© 2008 SCILLC. All rights reserved.
9
Characteristics subject to change without notice
Doc. No. MD-2114 Rev. K