DAC5687_15 Datasheet, PDF (32/80 Pages) Texas Instruments – 16-BIT, 500 MSPS 2´–8´ INTERPOLATING DUAL-CHANNEL DIGITAL-TO-ANALOG CONVERTER (DAC)

DAC5687
SLWS164E – FEBRUARY 2005 – REVISED SEPTEMBER 2006
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Serial Interface
The serial port of the DAC5687 is a flexible serial interface which communicates with industry standard
microprocessors and microcontrollers. The interface provides read/write access to all registers used to define the
operating modes of the DAC5687. It is compatible with most synchronous transfer formats and can be configured
as a three- or four-pin interface by sif_4pin in register CONFIG3. In both configurations, SCLK is the serial
interface input clock and SDENB is serial interface enable. For three-pin configuration, SDIO is a bidirectional pin
for both data in and data out. For four-pin configuration, SDIO is data in only and SDO is data out only.
Each read/write operation is framed by signal SDENB (serial data enable bar) asserted low for 2 to 5 bytes,
depending on the data length to be transferred (1–4 bytes). The first frame byte is the instruction cycle, which
identifies the following data transfer cycle as read or write, how many bytes to transfer, and what address to
transfer the data. Table 6 indicates the function of each bit in the instruction cycle and is followed by a detailed
description of each bit. Frame bytes 2 to 5 comprise the data transfer cycle.
Table 6. Instruction Byte of the Serial Interface
MSB
LSB
Bit
7
6
5
4
3
2
1
0
Description
R/W
N1
N0
A4
A3
A2
A1
A0
R/W Identifies the following data transfer cycle as a read or write operation. A high indicates a read operation
from the DAC5687, and a low indicates a write operation to the DAC5687.
[N1:N0] Identifies the number of data bytes to be transferred, per Table 7. Data is transferred MSB first. With
multibyte transfers, [A4:A0] is the address of the first data byte, and the address is decremented for each
subsequent byte.
Table 7. Number of Transferred Bytes Within One
Communication Frame
N1
N0
0
0
0
1
1
0
1
1
Description
Transfer 1 Byte
Transfer 2 Bytes
Transfer 3 Bytes
Transfer 4 Bytes
[A4:A0] Identifies the address of the register to be accessed during the read or write operation. For multibyte
transfers, this address is the starting address. Note that the address is written to the DAC5687 MSB first.
Figure 33 shows the serial interface timing diagram for a DAC5687 write operation. SCLK is the serial interface
clock input to the DAC5687. Serial data enable SDENB is an active-low input to the DAC5687. SDIO is serial
data in. Input data to the DAC5687 is clocked on the rising edges of SCLK.
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