3

FN8164.7

August 17, 2015

Pin Descriptions

Host Interface Pins

Serial Clock (SCL)

The SCL input is used to clock data into and out of the

X9241A.

Serial Data (SDA)

SDA is a bidirectional pin used to transfer data into and out

of the device. It is an open drain output and may be wire-

ORed with any number of open drain or open collector

outputs. An open drain output requires the use of a pull-up

resistor. For selecting typical values, refer to the guidelines

for calculating typical values on the bus pull-up resistors

graph.

Address

The Address inputs are used to set the least significant

4-bits of the 8-bit slave address. A match in the slave

address serial data stream must be made with the Address

input in order to initiate communication with the X9241A.

Potentiometer Pins

connections on either end of a mechanical potentiometer.

The wiper outputs are equivalent to the wiper output of a

mechanical potentiometer.

Pinout

X9241A

(20 LD DIP, SOIC, TSSOP)

TOP VIEW

Principles of Operation

The X9241A is a highly integrated microcircuit incorporating

four resistor arrays, their associated registers and counters

and the serial interface logic providing direct communication

between the host and the XDCP potentiometers.

Serial Interface

The X9241A supports a bidirectional bus oriented protocol.

The protocol defines any device that sends data onto the

bus as a transmitter and the receiving device as the receiver.

The device controlling the transfer is a master and the

device being controlled is the slave. The master will always

initiate data transfers and provide the clock for both transmit

and receive operations. Therefore, the X9241A will be

considered a slave device in all applications.

Clock and Data Conventions

Data states on the SDA line can change only during SCL

are reserved for indicating start and stop conditions.

Start Condition

All commands to the X9241A are preceded by the start

condition, which is a HIGH to LOW transition of SDA while

SDA and SCL lines for the start condition and will not

respond to any command until this condition is met.

Stop Condition

All communications must be terminated by a stop condition,

which is a LOW to HIGH transition of SDA while SCL is

HIGH.

Acknowledge

Acknowledge is a software convention used to provide a

positive handshake between the master and slave devices

on the bus to indicate the successful receipt of data. The

transmitting device, either the master or the slave, will

release the SDA bus after transmitting 8-bits. The master

generates a ninth clock cycle and during this period the

receiver pulls the SDA line LOW to acknowledge that it

successfully received the 8-bits of data. See Figure 7.

The X9241A will respond with an acknowledge after

recognition of a start condition and its slave address and

once again after successful receipt of the command byte. If

the command is followed by a data byte the X9241A will

respond with a final acknowledge.

Pin Names

SYMBOL

DESCRIPTION

SCL

Serial Clock

SDA

Serial Data

A0 to A3

Address

A0

A2

SDA

1

2

3

4

5

6

7

8

9

10

20

19

18

17

16

15

14

13

12

11

A1

A3

SCL

X9241A

Potentiometer Pins (terminal equivalent)

Pin Names

SYMBOL

DESCRIPTION

X9241A