CAT5251_13 Datasheet, PDF (9/15 Pages) ON Semiconductor – Quad Digital Potentiometer (POT)

CAT5251
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 13. INSTRUCTION SET (Note: 1/0 = data is one or zero)
Instruction Set
Instruction
I3 I2 I1 I0 R1 R0 WCR1/P1
Read Wiper Control 1 0 0 1 0 0
1/0
Register
Write Wiper Control 1 0 1 0 0 0
1/0
Register
Read Data Register 1 0 1 1 1/0 1/0
1/0
Write Data Register 1 1 0 0 1/0 1/0
1/0
XFR Data Register
1 1 0 1 1/0 1/0
1/0
to Wiper Control
Register
XFR Wiper Control
1 1 1 0 1/0 1/0
1/0
Register to Data
Register
Global XFR Data
0 0 0 1 1/0 1/0
0
Registers to Wiper
Control Registers
Global XFR Wiper
1 0 0 0 1/0 1/0
0
Control Registers to
Data Register
Increment/Decrement 0 0 1 0 0 0
1/0
Wiper Control Register
Read Status (WIP bit) 0 1 0 1 0 0
0
WCR0/P0
1/0
1/0
1/0
1/0
1/0
1/0
0
0
1/0
1
Operations
Read the contents of the Wiper Control Register
pointed to by P1−P0
Write new value to the Wiper Control Register
pointed to by P1−P0
Read the contents of the Data Register pointed to
by P1−P0 and R1−R0
Write new value to the Data Register pointed to
by P1−P0 and R1−R0
Transfer the contents of the Data Register
pointed to by P1−P0 and R1−R0 to its
associated Wiper Control Register
Transfer the contents of the Wiper Control
Register pointed to by P1−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 P1−P0
Read WIP bit to check internal write cycle status
The basic sequence of the three byte instructions is
illustrated in Figure 7. These three-byte instructions
exchange data between the WCR and one of the Data
Registers. The WCR controls the position of the wiper. The
response of the wiper to this action will be delayed by t_WRL.
A transfer from the WCR (current wiper position), to a Data
Register is a write to non-volatile memory and takes a
minimum of t_WR to complete. The transfer can occur
between one of the four potentiometers and one of its
associated registers; or the transfer can occur between all
potentiometers and one associated register.
Four instructions require a two-byte sequence to
complete, as illustrated in Figure 6. These instructions
transfer data between the host/processor and the CAT5251;
either between the host and one of the data registers or
directly between the host and the Wiper Control Register.
These instructions are:
 XFR Data Register to Wiper Control Register
This transfers the contents of one specified Data
Register to the associated Wiper Control Register.
 XFR Wiper Control Register to Data Register
This transfers the contents of the specified Wiper
Control Register to the specified associated Data
Register.
 Global XFR Data Register to Wiper Control
Register
This transfers the contents of all specified Data
Registers to the associated Wiper Control Registers.
 Global XFR Wiper Counter Register to Data
Register
This transfers the contents of all Wiper Control Registers
to the specified associated Data Registers.
Increment/Decrement Command
The final command is Increment/Decrement (Figures 8
and 9). The Increment/Decrement command is different
from the other commands. Once the command is issued the
master can clock the selected wiper up and/or down in one
segment steps; thereby providing a fine tuning capability to
the host. For each SCK clock pulse (t_HIGH) while SI is
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