CS5376
11. TIME BREAK FUNCTION
A time break event places a timing reference flag in
the output data stream. This flag is used during
post-processing to assign an absolute timing to the
digital samples and to time sync data from multiple
measurement channels.
To use the time break function, an externally gen-
erated timing reference signal is applied to the
TIMEB pin to initiate an internal sample counter.
After a certain number of output samples, pro-
grammed in the TIMEBRK register (0x29), the TB
flag is set in the status byte of the output data word
of all enabled channels. The TB flag is automatical-
ly cleared for the next data word, and appears for
only one output sample in each channel.
The programmable sample counter compensates
for group delay through the digital filters. When the
proper group delay is programmed into the TIME-
BRK register, the TB flag is set in the output data
word representing the instant the timing reference
signal was received. Without compensation for
group delay, the TB flag would be set in the output
data word immediately upon receipt and would
precede the sample for the timing reference signal.
guarantee the time break input is recognized by the
CS5376, it should be held a minimum of one mas-
ter clock period, nominally 32.768 MHz.
11.2 Time Break Delay
The TIMEBRK register (0x29) sets the delay be-
tween receiving the rising edge on the TIMEB pin
and output of the TB flag in the data stream. The
delay through the CS5376 digital filters depends on
several factors; the sinc filter decimation rate, the
number of coefficients in FIR1 and FIR2, and the
delay through the IIR filters.
The total group delay can be determined empirical-
ly by applying the timing reference signal rising
edge to both the TIMEB pin and the modulator an-
alog inputs. When a rising edge is received on the
TIMEB pin with no delay programmed into the
TIMEBRK register, the TB flag is set immediately
in the next output data word. After some delay, the
rising edge on the modulator inputs will be seen in
the output data stream. The total group delay of the
measurement channel is the number of samples be-
tween the TB flag being set and the appearance of
the impulse in the data stream.
11.1 Time Break Pin Description
TIMEB - Pin 57
Time break input pin. A rising edge on the TIMEB
pin signals the decimation engine to set the time
break (TB) flag in the output status word for the
sample representing the current sampling instant.
The rising edge can occur asynchronously to the
CS5376 and is handled as a priority interrupt. To
11.3 TB Flag Output
The time break flag (TB flag) marks the timing ref-
erence in the output data stream. The decimation
engine writes the TB flag to the status byte of the
SD port. The TB flag is set in all enabled conver-
sion channels for one output data word. See “Serial
Data Output Port” on page 71 for more information
about the SD port status byte.
TIMEB - Time Break, pin 57
Time break input. Signals the decimation engine to set the time break (TB) flag in the
output status word for the sample representing the current sampling instant.
Figure 48. Time Break Pin
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