DAC8574IPWR datasheet(18/45 Pages) TI

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Broadcast Address Byte

Control Byte

DAC8574

SLAS377B – JANUARY 2003 – REVISED DECEMBER 2004

MSB

LSB

Broadcast addressing is also supported by DAC8574. Broadcast addressing can be used for synchronously

updating or powering down multiple DAC8574 devices. DAC8574 is designed to work with other members of the

DAC857x and DAC757x families to support multichannel synchronous update. Using the broadcast address,

DAC8574 responds regardless of the states of the address pins. Broadcast is supported only in write mode

(Master writes to DAC8574).

MSB

LSB

Sel1

Sel0

PD0

Table 1. Control Register Bit Descriptions

Bit Name

Bit Number/Description

Extended Address Bit

The state of these bits must match the state of pins A3 and A2 in order for a

proper DAC8574 data update, except in broadcast update mode.

Extended Address Bit

Load1 (Mode Select) Bit

Are used for selecting the update mode.

Load0 (Mode Select) Bit

Store I2C data. The contents of MS-BYTE and LS-BYTE (or power down information) are stored in the

temporary register of a selected channel. This mode does not change the DAC output of the selected

channel.

Update selected DAC with I2C data. Most commonly utilized mode. The contents of MS-BYTE and

LS-BYTE (or power down information) are stored in the temporary register and in the DAC register of

the selected channel. This mode changes the DAC output of the selected channel with the new data.

4-Channel synchronous update. The contents of MS-BYTE and LS-BYTE (or power down information)

are stored in the temporary register and in the DAC register of the selected channel. Simultaneously,

the other three channels get updated with previously stored data from the temporary register. This

mode updates all four channels together.

Broadcast update mode. This mode has two functions. In broadcast mode, DAC8574 responds

regardless of local address matching, and channel selection becomes irrelevant as all channels update.

This mode is intended to enable up to 64 channels simultaneous update, if used with the I2C broadcast

address (1001 0000).

If Sel1=0

All four channels are updated with the contents of their temporary register

data.

If Sel1=1

All four channels are updated with the MS-BYTE and LS-BYTE data or

powerdown.

Sel1

Buff Sel1 Bit

Channel Select Bits

Sel0

Buff Sel0 Bit

Channel A

Channel B

Channel C

Channel D

PD0

Power Down Flag

Normal operation

Power-down flag (MSB7 and MSB6 indicate a power-down operation, as shown in Table 2).

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