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DAC7574

SLAS375 – JUNE 2003

Master Transmitter Writing to a Slave Receiver (DAC7574) in HS Mode

When writing data to the DAC7574 in HS-mode, the master begins to transmit what is called the HS-Master

Code

(0000 1XXX) in F/S-mode. No device is allowed to acknowledge the HS-Master Code, so the HS-Master

Code

is followed by a NOT acknowledge.

The master then switches to HS-mode and issues a repeated start condition, followed by the address byte (with

R/W = 0) after which the DAC7574 acknowledges by pulling SDA low. This address byte is usually followed by

the control byte, which is also acknowledged by the DAC7574. The LSB of the control byte (PD0-Bit) determines

if the following data is power-down data or regular data.

With (PD0-Bit = 0) the DAC7574 expects to receive data in the following sequence HIGH-BYTE – LOW-BYTE –

(refer to Table 5 HS-MODE WRITE SEQUENCE - DATA).

With (PD0-Bit = 1) the DAC7574 expects to receive 2 bytes of power-down data (refer to Table 5 HS-MODE

WRITE SEQUENCE - POWER DOWN).

Table 5. Master Transmitter Writes to Slave Receiver (DAC7574) in HS-Mode

HS MODE WRITE SEQUENCE - DATA

Transmitter

MSB

6

5

4

3

2

1

LSB

Comment

Master

Start

Begin sequence

Master

0

0

0

0

1

X

X

X

HS Mode Master Code

No device may acknowledge HS mas-

NONE

Not Acknowledge

ter code

Master

Repeated Start

Master

1

0

0

1

1

A1

A0

R/W

Write addressing (R/W=0)

DAC7574

DAC7574 Acknowledges

Master

0

0

Load 1

Load 0

0

Buff Sel 1

Buff Sel 0

PD0

Control byte (PD0=0)

DAC7574

DAC7574 Acknowledges

Master

D11

D10

D9

D8

D7

D6

D5

D4

Writing data word, MSB

DAC7574

DAC7574 Acknowledges

Master

D3

D2

D1

D0

x

x

x

x

Writing data word, LSB

DAC7574

DAC7574 Acknowledges

Master

Data or Stop or Repeated Start (1)

Data or done (2)

HS MODE WRITE SEQUENCE - POWER DOWN

Transmitter

MSB

6

5

4

3

2

1

LSB

Comment

Master

Start

Begin sequence

Master

0

0

0

0

1

X

X

X

HS Mode Master Code

No device may acknowledge HS mas-

NONE

Not Acknowledge

ter code

Master

Repeated Start

Master

1

0

0

1

1

A1

A0

R/W

Write addressing (R/W = 0)

DAC7574

DAC7574 Acknowledges

Master

0

0

Load 1

Load 2

0

Buff Sel 1

Buff Sel 0

PD0

Control Byte (PD0=1)

DAC7574

DAC7574 Acknowledges

Master

PD1

PD2

0

0

0

0

0

0

Writing data word, high byte

DAC7574

DAC7574 Acknowledges

Master

0

0

0

0

x

x

x

x

Writing data word, low byte

DAC7574

DAC7574 Acknowledges

Master

Stop or repeated start (1)

Done

(1)

Use repeated start to secure bus operation and loop back to the stage of write addressing for next Write.

(2)

Once DAC7574 is properly addressed and control byte is sent, high-byte-low-byte sequences can repeat until a stop or repeated start

condition is received.

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