cat5221 Catalyst Semiconductor, cat5221 Datasheet - Page 9

• Manufacturer Part Number: cat5221
• Description: Dual Digitally Programmable Potentiometers Dpp? With 64 Taps And I?c Interface
• Manufacturer: Catalyst Semiconductor

WIPER CONTROL AND DATA REGISTERS
Wiper Control Register (WCR)
The CAT5221 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 CAT5221 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
Note: 1/0 = data is one or zero
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
Instruction
Read Wiper Control
Register
Write Wiper Control
Register
Read Data Register
Write Data Register
XFR Data Register to
Wiper Control Register
XFR Wiper Control
Register to Data Register
Global XFR Data Registers
to Wiper Control Registers
Global XFR Wiper Control
Registers to Data Register
Increment/Decrement
Wiper Control Register
Instruction Set
I3
1 0 0 1 0
1 0 1 0 0
1 0 1 1 0
1 1 0 0 0
1 1 0 1 0
1 1 1 0 0
0 0 0 1 0
1 0 0 0 0
0 0 1 0 0
I2
I1 I0
0
WCR0/
1/0
1/0
1/0
1/0
1/0
1/0
1/0
P0
0
0
1/0
1/0
1/0
1/0
1/0
1/0
R1
0
0
0
9
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
— Write Wiper Control Register – change current
— Read Data Register – read the contents of the
— Write Data Register – write a new value to the
The basic sequence of the three byte instructions is
illustrated in Figure 8. These three-byte instructions
1/0
1/0
1/0
1/0
1/0
1/0
R0
0
0
0
wiper position of the selected potentiometer in
the WCR
wiper position in the WCR of the selected
potentiometer
selected Data Register
selected Data Register
Operation
Read the contents of the Wiper Control
Register pointed to by P0
Write new value to the Wiper Control Register
pointed to by P0
Read the contents of the Data Register
pointed to by P0 and R1-R0
Write new value to the Data Register pointed
to by P0 and R1-R0
Transfer the contents of the Data Register
pointed to by P0 and R1-R0 to its associated
Wiper Control Register
Transfer the contents of the Wiper Control
Register pointed to by 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 P0
Doc. No. MD-2113 Rev. K
CAT5221