GSE 60 SERIES Technical Reference Manual page 463

Table 12-6: Latency (Response Time) and Maximum Error
Periods Measured:
Input Freq (Hz)
1 0
5 0
1 0 0
5 0 0
1 , 0 0 0
5 , 0 0 0
1 0 , 0 0 0
2 0 , 0 0 0
5 0 , 0 0 0
Specifying a larger number of pulses results in a more accurate
measurement for a given frequency. However, the penalty is a longer time
period between updates of the calculated frequency. The measurement
error can be calculated using the following formula:
= −
f f
e s
where:
f = maximum error in frequency measurement.
e
f = frequency of signal being measured.
s
f = frequency of selected clock "A" or "B".
c
N = number of periods to measure.
Table 12-6 illustrates the latency (response time) and maximum error that
can be expected for various input frequencies and number of periods
measured:
1 period
Latency (s) Error (Hz) Latency (s) Error (Hz) Latency (s) Error (Hz)
0 . 1 0 0 0 0 0 0 . 0 0 0 1 9 1
0 . 0 2 0 0 0 0 0 . 0 0 4 7 6 8
0 . 0 1 0 0 0 0 0 . 0 1 9 0 7 0
0 . 0 0 2 0 0 0 0 . 4 7 6 3 8 3
0 . 0 0 1 0 0 0 1 . 9 0 3 7 1 8
0 . 0 0 0 2 0 0 4 7 . 2 3 3 2 6 4
0 . 0 0 0 1 0 0 ########
0 . 0 0 0 0 5 0 ########
0 . 0 0 0 0 2 0 ########
Note that there is no error for the pulse count. Every single pulse will be
counted within a few microseconds of when the specified edge (per P858)
has occurred.
However, the incoming signal must have clean transitions. If the input
signal is the result of a switch closure that experiences contact bounce,
then the bounces may be detected as extra pulses, resulting in a higher
than actual calculated frequency and pulse count.
P
HASE
The Phase Time function will measure the total high or low time for the
specified number of pulses. This can be used to determine the duty cycle
of an input signal if the frequency or period is known. Also, PhsTm
accumulates the total number of pulses which have occurred and this
count may be accessed at any time.
The setup parameters that pertain to the 'PhsTm' selection are:
N * f
c
N * f
+
c
1
f
s
1 0 p e r i o d s
1 . 0 0 0 0 0 0 0 . 0 0 0 0 1 9
0 . 2 0 0 0 0 0 0 . 0 0 0 4 7 7
0 . 1 0 0 0 0 0 0 . 0 0 1 9 0 7
0 . 0 2 0 0 0 0 0 . 0 4 7 6 7 9
0 . 0 1 0 0 0 0 0 . 1 9 0 6 9 8
0 . 0 0 2 0 0 0 4 . 7 6 3 8 2 8
0 . 0 0 1 0 0 0 1 9 . 0 3 7 1 7 6
0 . 0 0 0 5 0 0 7 6 . 0 0 4 0 1 3
0 . 0 0 0 2 0 0 ########
T (F
IME UNCTION
Programmable Digital I/O 12-17
1 0 0 periods
1 0 . 0 0 0 0 0 0
2 . 0 0 0 0 0 0
1 . 0 0 0 0 0 0
0 . 2 0 0 0 0 0
0 . 1 0 0 0 0 0
0 . 0 2 0 0 0 0
0 . 0 1 0 0 0 0
0 . 0 0 5 0 0 0
0 . 0 0 2 0 0 0 4 7 . 6 3 8 2 8 4
5)
60 Series Technical Reference Manual
0 . 0 0 0 0 0 2
0 . 0 0 0 0 4 8
0 . 0 0 0 1 9 1
0 . 0 0 4 7 6 8
0 . 0 1 9 0 7 3
0 . 4 7 6 7 9 2
1 . 9 0 6 9 8 5
7 . 6 2 6 4 8 5