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DAC7574

SLAS375 – JUNE 2003

Master Receiver Reading From a Slave Transmitter (DAC7574) in Standard/Fast Modes

When reading data back from the DAC7574, the user begins with an address byte (with R/W = 0) after which the

DAC7574 will acknowledge by pulling SDA low. This address byte is usually followed by the Control Byte, which

is also acknowledged by the DAC7574. 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 DAC7574, indicating that it is prepared to

transmit data. Two or three bytes of data are then read back from the DAC7574, 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 DAC7574 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 DAC7574 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)

DAC7574

DAC7574 Acknowledges

Master

0

0

Load 1

Load 0

x

Buff Sel 1

Buff Sel 0

PD0

Control byte (PD0=0)

DAC7574

DAC7574 Acknowledges

Master

Repeated Start

Master

1

0

0

1

1

A1

A0

R/W

Read addressing (R/W = 1)

DAC7574

DAC7574 Acknowledges

DAC7574

D11

D10

D9

D8

D7

D6

D5

D4

Reading data word, high byte

Master

Master Acknowledges

DAC7574

D3

D2

D1

D0

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)

DAC7574

DAC7574 Acknowledges

Master

0

0

Load 1

Load 0

x

Buff Sel 1

Buff Sel 0

PD0

Control byte (PD0=1)

DAC7574

DAC7574 Acknowledges

Master

Repeated Start

Master

1

0

0

1

1

A1

A0

R/W

Read addressing (R/W = 1)

DAC7574

DAC7574 Acknowledges

DAC7574

PD1

PD2

1

1

1

1

1

1

Read power down byte

Master

Master Acknowledges

DAC7574

D11

D10

D9

D8

D7

D6

D5

D4

Reading data word, high byte

Master

Master Acknowledges

DAC7574

D3

D2

D1

D0

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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