CS5376A datasheet(68/107 Pages) CIRRUS

68 / 107 page

CS5376A

18. TIME BREAK CONTROLLER

A time break signal is used to mark timing events

that occur during measurement. An external signal

sets a flag in the status byte of an output sample to

mark when the external event occurred.

A rising edge input to the TIMEB pin causes the

TB timing reference flag to be set in the SD port

status byte. When set, the TB flag appears for only

one output sample in the status byte of all enabled

channels. The TB flag output can be delayed by

programming a sample delay value into the TIME-

BRK digital filter register.

18.1 Pin Description

TIMEB - Pin 57

Time break input pin, rising edge triggered.

18.2 Time Break Operation

An externally generated timing reference signal ap-

plied to the TIMEB pin initiates an internal sample

counter. After a number of output samples have

passed, programmed in the TIMEBRK digital filter

of the SD port output word for all enabled channels.

The TB flag is automatically cleared for subse-

quent data words, and appears for only one output

sample in each channel.

18.3 Time Break Delay

The TIMEBRK register (0x29) sets a sample delay

between a received rising edge on the TIMEB pin

and writing the TB flag into the SD port status byte.

The programmable sample counter can compensate

for group delay through the digital filters. When the

proper group delay value is programmed into the

TIMEBRK register, the TB flag will be set in the

status byte of the measurement sample taken when

the timing reference signal was received.

18.3.1 Step Input and Group Delay

A simple method to empirically measure the step

response and group delay of a CS5376A measure-

ment channel is to use the time break signal as both

a timing reference input and an analog step input.

When a rising edge is received on the TIMEB pin

with no delay programmed into the TIMEBRK reg-

ister, the TB flag is set in the next SD port status

byte. The same rising edge can act as a step input to

the analog channel, propagating through the digital

filter to appear as a rising edge in the measurement

data. By comparing the timing of the TB status flag

output and the rising edge in the measurement data,

the measurement channel group delay can be deter-

mined.

TIMEB

in SD Port

Status Byte

Delay Counter

TIMEBRK

TB Flag

Figure 37. Time Break Block Diagram

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