Datasheet

ADS1281

SBAS378D –AUGUST 2007–REVISED JUNE 2010

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PIN AND REGISTER MODES SYNCHRONIZATION

(SYNC PIN AND SYNC COMMAND)

The PINMODE input (pin 21) is used to set the

control mode of the device: Pin mode or Register The ADS1281 can be synchronized to an external

mode. In Pin mode (PINMODE = 1), control of the event, as well as synchronized to other ADS1281

device is set by pins; there are no registers to devices if the sync event is applied simultaneously to

program. In Register mode, control of the device is all devices.

set by the configuration registers. As a result of the

The ADS1281 has two sources for synchronization:

increased flexibility provided by the register space,

the SYNC input pin and the SYNC command. The

ADS1281 also has two synchronizing modes:

describes the differences between the control modes.

Pulse-sync and Continuous-sync. In Pulse-sync

Table 10 summarizes the functions of the mode, the ADS1281 synchronizes to a single sync

dual-purpose pins, depending on the control mode event. In Continuous-sync mode, either the device

selected. synchronizes to a single sync event or a continuous

clock is applied to the pin with a period equal to

integer multiples of the data rate. When the periods of

the sync input and the DRDY output do not match,

the ADS1281 re-synchronizes and conversions are

restarted. Note that in Pin control mode, the RESET

input serves as the sync control.

Table 9. Functions for Pin Mode and Register Mode

PIN MODE REGISTER MODE

FUNCTION (PINMODE = 1) (PINMODE = 0)

Synchronization options Pulse only Continuous or Pulse

Digital filter options Sinc + LPF or Sinc + LPF + HPF Sinc, Sinc + LPF, or Sinc + LPF + HPF

Digital high-pass filter frequency Fixed low-cut as ratio of f

DATA

Programmable

Calibration registers No Yes

Interface commands No Yes

Table 10. Mode-Dependent Pin Functions

PIN MODE REGISTER MODE

PIN (PINMODE = 1) (PINMODE = 0)

MOD/DIN MOD input (select Modulator mode) SPI DIN input

HPF/SYNC HPF input (select high-pass filter) SYNC input

RESET Sync input Reset input

PHS/MCLK LPF phase input or MCLK output MCLK output

DR0/M0 DR0 input or M0 output M0 output

DR1/M1 DR1 input or M1 output M1 output

Product Folder Link(s): ADS1281