X9268 datasheet(11/22 Pages) RENESAS

11 / 22 page

X9268

FN8172 Rev.4.00

Page 11 of 22

August 29, 2006

DEVICE DESCRIPTION

Instructions

Four of the nine instructions are three 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 three byte instructions is

illustrated in Figure 4. These three-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 response of the wiper

to this action will be delayed by tWRL. A transfer from the

WCR (current wiper position), to a Data Register is a

write to nonvolatile memory and takes a minimum of tWR

to complete. The transfer can occur between one of the

four potentiometers and one of its associated registers;

or it may occur globally, where the transfer occurs

between all potentiometers and one associated register

Four instructions require a two-byte sequence to

complete. These instructions transfer data between the

host and the X9268; 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 Reg-

ister to the associated Wiper Counter Register.

– XFR Wiper Counter Register to Data Register –

This transfers the contents of the specified Wiper

Counter Register to the specified associated Data

– Global XFR Data Register to Wiper Counter

– This transfers the contents of all specified

Data Registers to the associated Wiper Counter Reg-

isters.

– Global XFR Wiper Counter Register to Data

– This transfers the contents of all Wiper

Counter Registers to the specified associated Data

Registers.

INCREMENT/DECREMENT COMMAND

The final command is Increment/Decrement (Figure 5

and 6). The Increment/Decrement command is different

from the other commands. Once the command is issued

and the X9268 has responded with an acknowledge, 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 SCL clock pulse (tHIGH)

while SDA is HIGH, the selected wiper will move one

resistor segment towards the RH terminal. Similarly, for

each SCL clock pulse while SDA is LOW, the selected

wiper will move one resistor segment towards the RL

terminal.

See Instruction format for more details.

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