Datasheet

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Master Transmitter Writing to a Slave Receiver (DAC8574) in HS Mode
DAC8574
SLAS377B – JANUARY 2003 – REVISED DECEMBER 2004
When writing data to the DAC8574 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 DAC8574 acknowledges by pulling SDA low. This address byte is usually followed by
the control byte, which is also acknowledged by the DAC8574. 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 DAC8574 expects to receive data in the following sequence HIGH-BYTE – LOW-BYTE –
HIGH-BYTE – LOW-BYTE...., until a STOP condition or repeated start condition on the I
2
C-Bus is recognized
(refer to Table 5 HS-MODE WRITE SEQUENCE - DATA).
With (PD0-Bit = 1) the DAC8574 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 (DAC8574) 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
NONE Not Acknowledge
master code
Master Repeated Start
Master 1 0 0 1 1 A1 A0 R/ W Write addressing ( R/ W=0)
DAC8574 DAC8574 Acknowledges
Master 0 0 Load 1 Load 0 0 Buff Sel 1 Buff Sel 0 PD0 Control byte ( PD0=0)
DAC8574 DAC8574 Acknowledges
Master D15 D14 D13 D12 D11 D10 D9 D8 Writing data word, MSB
DAC8574 DAC8574 Acknowledges
Master D7 D6 D5 D4 D3 D2 D1 D0 Writing data word, LSB
DAC8574 DAC8574 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
NONE Not Acknowledge
master code
Master Repeated Start
Master 1 0 0 1 1 A1 A0 R/ W Write addressing ( R/ W = 0)
DAC8574 DAC8574 Acknowledges
Master 0 0 Load 1 Load 2 0 Buff Sel 1 Buff Sel 0 PD0 Control Byte ( PD0=1)
DAC8574 DAC8574 Acknowledges
Master PD1 PD2 0 0 0 0 0 0 Writing data word, high byte
DAC8574 DAC8574 Acknowledges
Master 0 0 0 0 0 0 0 0 Writing data word, low byte
DAC8574 DAC8574 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 DAC8574 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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