ADS1258IPHPREP datasheet(33/57 Pages) TI

33 / 57 page

NOTES: (1)OptionalforAuto-Scanmode,disabledforFixed-Channelmode.SeeTable13,StatusByte.

(2)Afterthechanneldatareadoperation,

mustbetoggledoranSPItimeoutmustoccurbeforesendingcommands.

(3)NoSCLKactivity.

(3)

DRDY

SCLK

DOUT

DIN

(holdinactive)

StatusByte

(1)

DataByte1(MSB)

DataByte3(MSB)

(2)

ADS1258-EP

www.ti.com

SBAS445C – MARCH 2009 – REVISED DECEMBER 2009

write operations in progress will terminate and the

may be read at any time without concern to DRDY.

SPI interface resets. This timeout feature can be

The NEW bit of the STATUS byte indicates that the

used to recover lost communication when a serial

data register has been refreshed with new converter

interface transmission is interrupted or inadvertently

data since the last read operation. The data is shifted

glitched.

out MSB first after the STATUS byte.

It should be noted that on system power-up, if the

Data Input (DIN) and Data Output (DOUT)

ADS1258 interface signals are floating or undefined,

Operation

the interface could wake in an unknown state. This

The data input pin (DIN) is used to input data to the

condition is remedied by resetting the interface in

ADS1258. The data output pin (DOUT) is used to

three ways: toggle the RESET pin low then high;

output data from the ADS1258. Data on DIN is shifted

toggle the CS pin high then low; or hold SCLK

into the converter on the rising edge of SCLK while

inactive for 218 + 4096 fCLK cycles.

data is shifted out on DOUT on the falling edge of

SCLK. DOUT is tri-stated when CS is high to allow

Channel Data Read Direct

multiple devices to share the line.

Channel data can be accessed from the ADS1258 in

two ways: Direct data read or data read with register

SPI Bus Sharing

format. With Direct read, the DIN input pin is held

The ADS1258 can be connected to a shared SPI bus.

inactive (high or low) for at least the first three SCLK

DOUT tri-states when CS is deselected (high). When

transitions. When the first three bits are 000 or 111,

the ADS1258 is connected to a shared bus, data can

the device detects a direct data read and channel

be read only by the Channel Data Read command

data is output. After the device defects this read

format.

format, commands are ignored until either CS is

toggled, an SPI timeout occurs or the device is reset.

COMMUNICATION PROTOCOL

The Channel Data Read command does not have

this requirement.

Communicating to the ADS1258 involves shifting data

into the device (via the DIN pin) or shifting data out of

Concurrent with the first SCLK transition, channel

the device (via the DOUT pin) under control of the

data is output on the DOUT output pin. A total of 24

SCLK input.

or 32 SCLK transitions complete the data read

operation. The number of shifts depend on whether

Reading DATA

the status byte is enabled. The data must be

completely shifted out before the next occurrence of

DRDY goes low to indicate that new conversion data

DRDY or the remaining data will be corrupted. It is

is ready. The data may be read via a direct data read

recommended to monitor DRDY to synchronize the

(Channel Data Read Direct) or the data may be read

start of the read operation to avoid data corruption.

in a register format (Channel Data Read Register). A

Before DRDY asserts low, the MSB of the Status byte

direct data read requires the data to be read before

or the MSB of the data is output on DOUT (CS = '0'),

the next occurrence of DRDY or the data will be

as shown in Figure 58. In this format, reading the

corrupted.

This

type

data

read

requires

data a second time within the same DRDY frame

synchronization with DRDY to avoid this conflict.

returns data = 0.

When reading data in the register format, the data

Figure 58. Channel Data Read Direct (No Command)

Submit Documentation Feedback

Product Folder Link(s): ADS1258-EP

ADS1258IPHPREP Datasheet(PDF) 33 Page - Texas Instruments

ADS1258IPHPREP Datasheet(HTML) 33 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57

Datasheet Download

Link URL