ADS5400IPZP datasheet(16/50 Pages) TI

16 / 50 page

ADS5400

SLAS611B – OCT 2009 – REVISED MARCH 2010

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SERIAL INTERFACE

The serial port of the ADS5400 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 ADS5400. It is compatible with most synchronous transfer formats and can be configured as

a 3 or 4 pin interface in register 0x01h. In both configurations, SCLK is the serial interface input clock and

SDENB is serial interface enable. For 3 pin configuration, SDIO is a bidirectional pin for both data in and data

out. For 4 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 3 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 3. Instruction Byte of the Serial Interface

MSB

LSB

Bit

Description

R/W

Identifies the following data transfer cycle as a read or write operation. A high indicates a read

operation from ADS5400 and a low indicates a write operation to the ADS5400.

[N1:N0]

Identifies the number of data bytes to be transferred per Table 4 below. Data is transferred MSB

first.

Table 4. Number of Transferred Bytes Within One

Communication Frame

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

multi-byte transfers, this address is the starting address. Note that the address is written to the

ADS5400 MSB first and counts down for each byte.

Figure 6 shows the serial interface timing diagram for a ADS5400 write operation. SCLK is the serial interface

clock input to ADS5400. Serial data enable SDENB is an active low input to ADS5400. SDIO is serial data in.

Input data to ADS5400 is clocked on the rising edges of SCLK.

Product Folder Link(s): ADS5400

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