X9448 Datasheet, PDF(8/19 Page) Xicor Inc. – Mixed Signal with 2-Wire Interface

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X9448 Datasheet, PDF (8/19 Pages) Xicor Inc. – Mixed Signal with 2-Wire Interface

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X9448

REGISTERS OPERATION

Both XDCP potentiometers and voltage comparators

share the serial interface and share a common archi-

tecture. Each potentiometer and voltage comparator is

associated with wiper counter and analog control reg-

isters and eight data registers. A detailed discussion of

the register organization and array operation follows.

Wiper Counter (WCR) and Analog Control

Registers (ACR)

The X9448 contains two wiper counter registers one

for each XDCP potentiometer and two analog control

registers, one for each of the two voltage comparators.

The wiper counter register is equivalent to a serial-in,

parallel-out counter with its outputs decoded to select

one of sixty-four switches along its resistor array. The

contents of the wiper counter register and analog con-

trol register can be altered in four ways: it may be writ-

ten directly by the host via the Write WCR instruction

(serial load); it may be written indirectly by transferring

the contents of one of four associated data registers

(DR) via the XFR data register instruction (parallel

load); it can be modified one step at a time by the

increment/decrement instruction (WCR only). Finally,

it is loaded with the contents of its data register zero

(R0) upon power-up.

The wiper counter and analog control register are vol-

atile registers; that is, their contents are lost when the

X9448 is powered-down. Although the registers are

automatically loaded with the value in R0 upon power-

up, it should be noted this may be different from the

value present at power-down.

Programming the ACR is similar to the WCR. How-

ever, the 6 bits in the WCR positions the wiper in the

resistor array while 3 bits in the ACR control the com-

parator and its output.

Data Registers (DR)

Each potentiometer and each voltage comparator has

four nonvolatile data registers (DR). These can be

read or written directly by the host and data can be

transferred between any of the four data registers and

the WCR or ACR. It should be noted all operations

changing data in one of these 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 or comparator, these

registers can be used as regular memory locations that

could store system parameters or user preference data.

Wiper Counter Register (WCR)

0 0 WP5 WP4 WP3 WP2 WP1 WP0

(volatile)

(LSB)

WP0-WP5 identify wiper position.

Analog Control Register (ACR)

User User User

Shut-

0 0 -bit5 -bit4 -bit3 Latch Enable down

(volatile)

(LSB)

Shutdown

â1â indicates power is connected to the voltage

comparator.

â0â indicates power is not connected to the voltage

comparator.

Enable

â1â indicates the output buffer of the voltage com-

parator is enabled.

â0â indicates the output buffer of the voltage com-

parator is disabled.

Latch

â1â indicates the output of the voltage comparator

is memorized or latched.

â0â indicates the output of the voltage comparator

is not latched.

Userbitsâavailable for user applications

Data Registers (DR, R0 - R3)

Wiper Position or Analog Control Data or User Data

(Nonvolatile)

Memory Map

WCRO

WCR1

ACR0

ACR1

FN8201.0

April 18, 2005

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