7

FN8162.4

July 9, 2008

Instruction and Register Description

Device Addressing

WIPER COUNTER REGISTER (WCR)

The X9119 contains a Wiper Counter Registers (refer to

Table 4) for the XDCP potentiometer. The WCR is equivalent

to a serial-in, parallel-out register/counter with its outputs

decoded to select one of 1024 switches along its resistor

array. The contents of the WCR can be altered in one of

three ways:

1. it may be written directly by the host via the write wiper

counter register instruction (serial load)

2. it may be written indirectly by transferring the contents of

one of four associated data registers via the XFR data

register

3. it is loaded with the contents of its data register zero (R0)

upon power-up.

The Wiper Counter Register is a volatile register; that is, its

contents are lost when the X9119 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. Power-up guidelines are

recommended to ensure proper loadings of the DR0 value

into the WCR.

DATA REGISTERS (DR0 TO DR3)

The potentiometer has four 10-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 Wiper Counter Register. All operations

changing data in one of the data registers is a nonvolatile

operation and will take a maximum of 10ms.

If the application does not require storage of multiple

settings for the potentiometer, the Data Registers can be

used as regular memory locations for system parameters or

user preference data.

Bit 9–Bit 0 are used to store one of the 1024 wiper position

(0 ~1023).

TABLE 4. WIPER CONTROL REGISTER, WCR (10-BIT), WCR9–WCR0: Used to store the current wiper position (Volatile, V)

TABLE 5. DATA REGISTER, DR (10-BIT), BIT 9–BIT 0: Used to store wiper positions or data (Non-Volatile, NV)

Four of the six instructions are four bytes in length. These

instructions are:

• Read Wiper Counter Register – read the current wiper

position of the selected potentiometer,

• Write Wiper Counter Register – change current wiper

position 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 four byte instructions is illustrated

in Figure 3. These four-byte instructions exchange data

between the WCR and one of the Data Registers. A transfer

from a data register to a WCR is essentially a write to a static

RAM, with the static RAM controlling the wiper position. The

A transfer from the WCR (current wiper position), to a data

register is a write-to-nonvolatile memory and takes a

between one of the four potentiometers and one of its

associated registers.

Two instructions (Figure 4) require a two-byte sequence to

complete. These instructions transfer data between the host

and the X9119; either between the host and one of the data

registers or directly between the host and the Wiper Counter

Register. These instructions are:

• XFR Data Register to Wiper Counter Register – This

transfers the contents of one specified Data Register to

the Wiper Counter Register.

• XFR Wiper Counter Register to Data Register – This

transfers the contents of the Wiper Counter Register to the

specified Data Register.

See “Instruction Format” on page 8 for more details.

POWER-UP AND DOWN REQUIREMENTS

and the voltages applied to the potentiometer pins provided

are no restrictions on the power-down condition. However,

the datasheet parameters for the DCP do not apply until 1ms

WCR9

WCR8

WCR7

WCR6

WCR5

WCR4

WCR3

WCR2

WCR1

WCR0

VVVVVVVVVV

(MSB)

(LSB)

Bit 9

Bit 8

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

NV

NV

NV

NV

NV

NV

NV

NV

NV

NV

MSB

LSB

X9119