www.ti.com

SLAVE ADDRESS R/W

A Ctrl-Byte

A MS-Byte A

LS-Byte

A/A

P

”0” (write)

Data Transferred

(n* Words + Acknowledge)

Word = 12 Bit

From Master to DAC7574

From DAC7574 to Master

A = Acknowledge (SDA LOW)

A = Not Acknowledge (SDA HIGH)

S = START Condition

Sr = Repeated START Condition

P = STOP Condition

1

0

0

1

1

A1

A0

R/W

MSB

LSB

Factory Preset

S

‘0’ = Write to DAC7574

‘1’ = Read from DAC7574

DAC7574

SLAS375 – JUNE 2003

LDAC Functionality

Depending on the control byte, DACs are synchronously updated on the falling edge of the acknowledge signal

that follows LS byte. The LDAC pin is required only when an external timing signal is used to update all the

channels of the DAC asynchronously. LDAC is a positive edge triggered asynchronous input that allows four

DAC output voltages to be updated simultaneously with temporary register data. The LDAC trigger should only

be used after the buffers temporary registers are properly updated through software.

DAC7574 Registers

Table 3. DAC7574 Architecture Register Descriptions

Register

Description

CTRL[7:0]

Stores 8-bit wide control byte sent by the master

Stores the 8 most significant bits of unsigned binary data sent by the master. Can also store 2-bit

MSB[7:0]

power-down data.

LSB[7:0]

Stores the 4 least significant bits of unsigned binary data sent by the master.

TRA[13:0], TRB[13:0],

14-bit temporary storage registers assigned to each channel. Two MSBs store power-down information, 12

TRC[13:0], TRD[13:0]

LSBs store data.

DRA[13:0], DRB[13:0],

14-bit DAC registers for each channel. Two MSBs store power-down information, 12 LSBs store DAC data.

DRC[13:0], DRD[13:0]

An update of this register means a DAC update with data or power-down.

DAC7574 as a Slave Receiver - Standard and Fast Mode

Figure 35 shows the standard and fast mode master transmitter addressing a DAC7574 Slave Receiver with a

7-bit address.

Figure 35. Standard and Fast Mode: Slave Receiver

17