X9250 datasheet(4/21 Pages) XICOR

4 / 21 page

X9250

Characteristics subject to change without notice.

4 of 21

REV 1.1.5 1/31/03

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Write in Process

The contents of the Data Registers are saved to

nonvolatile memory when the CS pin goes from LOW

to HIGH after a complete write sequence is received

by the device. The progress of this internal write

operation can be monitored by a write in process bit

(WIP). The WIP bit is read with a read status

command.

INSTRUCTIONS

Identification (ID) Byte

The ﬁrst byte sent to the X9250 from the host,

following a CS going HIGH to LOW, is called the

Identiﬁcation byte. The most signiﬁcant four bits of the

slave address are a device type identiﬁer, for the

X9250 this is ﬁxed as 0101[B] (refer to Figure 2).

The two least signiﬁcant bits in the ID byte select one

of four devices on the bus. The physical device

address is deﬁned by the state of the A0-A1 input pins.

The X9250 compares the serial data stream with the

address input state; a successful compare of both

address bits is required for the X9250 to successfully

continue the command sequence. The A0–A1 inputs

can be actively driven by CMOS input signals or tied to

VCC or VSS.

The remaining two bits in the slave byte must be set to 0.

Figure 2. Identification Byte Format

Instruction Byte

The next byte sent to the X9250 contains the

instruction and register pointer information. The four

most signiﬁcant bits are the instruction. The next four

bits point to one of the four pots and, when applicable,

they point to one of four associated registers. The

format is shown below in Figure 3.

Figure 3. Instruction Byte Format

Device Type

Identifier

Device Address

Pot Select

Select

Instructions

Figure 1. Detailed Potentiometer Block Diagram

Serial Data Path

From Interface

Circuitry

Serial

Bus

Input

Parallel

Input

Counter

Inc/Dec

Logic

UP/DN

CLK

Modified SCK

UP/DN

VH/RH

VL/RL

VW/RW

If WCR = 00[H] then VW/RW = VL/RL

If WCR = FF[H] then VW/RW = VH/RH

Wiper

(One of Four Arrays)

(WCR)

Bus

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