CAT5419 Datasheet, PDF (9/18 Pages) Catalyst Semiconductor – Dual Digitally Programmable Potentiometers (DPP) with 64 Taps and 2-wire Interface

CAT5419
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
Table 3. Instruction Set
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
The basic sequence of the three byte instructions is
illustrated in Figure 8. These three-byte instructions
Instruction
I3
Read Wiper Control
1
Register
Write Wiper Control Register 1
Instruction Set
I2 I1 I0 R1 R0
001 00
010 00
Read Data Register
1 0 1 1 1/0 1/0
Write Data Register
1 1 0 0 1/0 1/0
XFR Data Register to Wiper 1 1 0 1 1/0 1/0
Control Register
XFR Wiper Control Register 1 1 1 0 1/0 1/0
to Data Register
Gang XFR Data Registers
to Wiper Control Registers
0 0 0 1 1/0 1/0
Gang XFR Wiper Control
Registers to Data Register
1 0 0 0 1/0 1/0
Increment/Decrement Wiper 0 0 1 0 0 0
Control Register
Note: 1/0 = data is one or zero
WCR0/
0
P0
Operation
0
1/0 Read the contents of the Wiper Control
Register pointed to by P0
0
1/0 Write new value to the Wiper Control
Register pointed to by P0
0
1/0 Read the contents of the Data Register
pointed to by P0 and R1-R0
0
1/0 Write new value to the Data Register
pointed to by P0 and R1-R0
0
1/0 Transfer the contents of the Data Register
pointed to by P0 and R1-R0 to its
associated Wiper Control Register
0
1/0 Transfer the contents of the Wiper Control
Register pointed to by P0 to the Data
Register pointed to by R1-R0
0
0 Transfer the contents of the Data Registers
pointed to by R1-R0 of both pots to their
respective Wiper Control Register
0
0 Transfer the contents of both Wiper Control
Registers to their respective data Registers
pointed to by R1-R0 of both pots
0
1/0 Enable Increment/decrement of the Control
Latch pointed to by P0
9
Document No. 2115, Rev. F