Cirrus Logic CS5376A - Manual (Page 67)

CS5376A
DS612F4 67
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
register (0x29), the TB flag is set in the status byte
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 35. Time Break Block Diagram