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Master Receiver Reading From a Slave Transmitter (DAC6574) in Standard/Fast Modes

DAC6574

SLAS408 – DECEMBER 2003

When reading data back from the DAC6574, the user begins with an address byte (with R/W = 0) after which the

DAC6574 will acknowledge by pulling SDA low. This address byte is usually followed by the Control Byte, which

is also acknowledged by the DAC6574. Following this there is a REPEATED START condition by the Master and

the address is resent with (R/W = 1). This is acknowledged by the DAC6574, indicating that it is prepared to

transmit data. Two or three bytes of data are then read back from the DAC6574, depending on the (PD0-Bit).

The value of Buff-Sel1 and Buff-Sel0 determines, which channel data is read back. A STOP Condition follows.

With the (PD0-Bit = 0) the DAC6574 transmits 2 bytes of data, HIGH-BYTE followed by the LOW-BYTE (refer to

Table 2. Data Readback Mode - 2 bytes).

With the (PD0-Bit = 1) the DAC6574 transmits 3 bytes of data, POWER-DOWN-BYTE followed by the

HIGH-BYTE followed by the LOW-BYTE (refer to Table 2. Data Readback Mode - 3 bytes).

Table 6. Read Sequence in F/S Mode

DATA READBACK MODE - 2 BYTES

Transmitter

MSB

6

5

4

3

2

1

LSB

Comment

Master

Start

Begin sequence

Master

1

0

0

1

1

A1

A0

R/W

Write addressing (R/W=0)

DAC6574

DAC6574 Acknowledges

Master

0

0

Load 1

Load 0

x

Buff Sel 1

Buff Sel 0

PD0

Control byte (PD0=0)

DAC6574

DAC6574 Acknowledges

Master

Repeated Start

Master

1

0

0

1

1

A1

A0

R/W

Read addressing (R/W = 1)

DAC6574

DAC6574 Acknowledges

DAC6574

D9

D8

D7

D6

D5

D4

D3

D2

Reading data word, high byte

Master

Master Acknowledges

DAC6574

D1

D0

x

x

x

x

x

x

Reading data word, low byte

Master

Master Not Acknowledges

Master signal end of read

Master

Stop or Repeated Start(1)

Done

DATA READBACK MODE - 3 BYTES

Transmitter

MSB

6

5

4

3

2

1

LSB

Comment

Master

Start

Begin sequence

Master

1

0

0

1

1

A1

A0

R/W

Write addressing (R/W=0)

DAC6574

DAC6574 Acknowledges

Master

0

0

Load 1

Load 0

x

Buff Sel 1

Buff Sel 0

PD0

Control byte (PD0=1)

DAC6574

DAC6574 Acknowledges

Master

Repeated Start

Master

1

0

0

1

1

A1

A0

R/W

Read addressing (R/W = 1)

DAC6574

DAC6574 Acknowledges

DAC6574

PD1

PD2

1

1

1

1

1

1

Read power down byte

Master

Master Acknowledges

DAC6574

D9

D8

D7

D6

D5

D4

D3

D2

Reading data word, high byte

Master

Master Acknowledges

DAC6574

D1

D0

x

x

x

x

x

x

Reading data word, low byte

Master

Master Not Acknowledges

Master signal end of read

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.

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