Mitsubishi Electric MELSEC-L02SCPU User Manual page 196

(a) Internal clock
By setting the internal clock, clock frequencies generated at the inside of the LCPU can be counted as input
pulses. For example, when the internal clock is used together with the coincidence output function, an on delay
timer can be configured.
Ex.
Selecting "Internal Clock (100s)" in Count Source Selection and turning on Coincidence output No.1
signal after the elapse of 180 seconds
CH1 current value (SD1880, SD1881)
1800000
900000
0
A count value and time have the following relationship.
Count value
Remark
The accuracy of measured time against a count value is as follows.
Count source
Internal Clock (0.1s)
Internal Clock (1s)
Internal Clock (10s)
Internal Clock (100s)
194
90
Set Coincidence output No.1 point setting to 1800000 and
start counting an internal clock (100 s).
Time (s)
=
Internal clock ( s)
60ppm and "-6.25ns to +9.376ns"
(Example) When pulses are counted from 0 to 10000, time calculated using a count value
is: 1ms (= (10000 - 0)  0.1s). However, the measured time will be as follows:
(1ms  (1-0.00006) - 6.25ns) to (1ms  (1 + 0.00006) + 9.376ns)
60ppm
When the count reaches to
1800000 (180s), Coincidence
output No.1 signal turns on.
t(s)
180
Time accuracy