IDEC MICROSmart FC6A Series Ladder Programming Manual page 106

4: B I
ASIC NSTRUCTIONS
Timer Counting Error
Every timer instruction operation is individually based on asynchronous 16-bit reference timers. Therefore, an error can occur
depending on the status of the asynchronous 16-bit timer when the timer instruction is executed. Use of a TMS (1-ms timer) is
recommended to reduce advance errors.
Error
Advance error
Maximum
Behind error
Timeout Output Error
The output RAM status is set to the actual output when the END instruction is processed. When timeout output turns from off to
on, an error occurs depending on the position where the timer instruction is programmed in the user program. The timeout output
error shown below does not include output delay caused by the hardware.
Program Processing
Timeout Output RAM
Actual Output
Error Maximum and Minimum
Error
Advance error
Minimum
Behind error
Advance error
Maximum
Behind error
Notes: Advance error does not occur at the timer input and timeout output.
Tet + Tte = 1 scan time
Increment is 1 s (TML), 100 ms (TIM), 10 ms (TMH), or 1 ms (TMS).
The maximum advance error is: Increment – 1 scan time
The maximum behind error is: 3 scan times
The timer input error and timeout output error shown above do not include the input response time (behind error) and output response
time (behind error) caused by hardware.
Power Failure Memory Protection
Timers TML, TIM, TMH, and TMS do not have power failure protection. To provide a timer with this protection use a counter
instruction and special internal relay M8121 (1-s clock), M8122 (100-ms clock), or M8123 (10-ms clock).
Ladder Diagram
(10-s Timer)
Reset
CNT C2
1000
I1
Pulse
M8123
4-10
TML
(1-s timer)
1,000 ms
1 scan time
END TIM
ON
OFF
ON
OFF
Tte
1 scan time
Timer Input Error
0 (Note)
Tet + Tie
0 (Note)
1 scan time +
Tet (1 scan time)
Program List
Instruction
LODN
LOD
CNT
Note: Designate counter C2 used in this program as a keep type counter. See Chapter 5 "Memory Backup" in
the "FC6A Series MICROSmart User's Manual".
FC6A S MICROS
ERIES MART
TIM
(100-ms timer)
100 ms
1 scan time
END
Timeout output error is equal to Tte (behind error) and can be between
0 and one scan time.
0 < Tte < 1 scan time
Tte: Time from the timer instruction execution to the END processing
Timer Counting Timeout Output
Error
0
0
Increment
1 scan time
Data
I1
M8123
C2
1000
L P M
ADDER ROGRAMMING ANUAL
TMH
(10-ms timer)
10 ms
1 scan time
Error
0 (Note)
Tte
0 (Note) Increment – (Tet + Tte)
Tte (1 scan time) 2 scan times + (Tet + Tte)
Timing Chart
ON
I1
OFF
10 s
ON
C2
OFF
FC9Y-B1726
TMS
(1-ms timer)
1 ms
1 scan time
Total Error
0
0