DAC0854CIWM datasheet(10/14 Pages) NSC

10 / 14 page

Digital Interface

The DAC0854 has two interface modes a WRITE mode

and a READ mode The WRITE mode is used to convert an

8-bit digital input word into a voltage The READ mode is

used to read back the digital data that was sent to one or all

of the DACs These modes are selected by the appropriate

setting of the RDWR bit which is part of the instruction

byte The instruction byte precedes the data byte at the DI

pin In both modes a high level on the Start Bit (SB) alerts

the DAC to respond to the remainder of the input stream

Table I lists the instruction set for the WRITE mode when

writing to only a single DAC and Table II lists the instruction

set for a global write The DACs are always written to LSB

first All DACs will be written to if the global bit (G) is high

DAC 1 is written to first then DACs 2 3 and 4 (in that order)

If the update bit is high then the DAC output will be updated

on the rising edge of CS otherwise the new data byte will

be placed only in the input register Chip Select (CS) must

remain low for at least one clock cycle after the last data bit

has been entered (See

Figures 1 and 2 )

TABLE I WRITE Mode Instruction Set (Writing to a Single DAC)

RDWR

Description

Bit

3 Bit

4 Bit

5 Bit

0000

Write DAC 1 no update of DAC outputs

0001

Write DAC 2 no update of DAC outputs

0010

Write DAC 3 no update of DAC outputs

0011

Write DAC 4 no update of DAC outputs

0100

Write DAC 1 update DAC 1 on CS rising edge

0101

Write DAC 2 update DAC 2 on CS rising edge

0110

Write DAC 3 update DAC 3 on CS rising edge

0111

Write DAC 4 update DAC 4 on CS rising edge

TABLE II WRITE Mode Instruction Set (Writing to all DACs)

RDWR

Description

Bit

Write all DACs no update of outputs

Write all DACs update all outputs on CS rising edge

DAC0854CIWM Datasheet(PDF) 10 Page - National Semiconductor (TI)

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