7: B
ASIC
I
NSTRUCTIONS
O
PEN
N
ET
C
ONTROLLER
U
SER
’
S
M
ANUAL
7-9
Timer Circuit
The preset value 0 through 65535 can be designated using a data register D0 through D7999; then the data of the data reg-
ister becomes the preset value. Directly after the TML, TIM, TMH, or TMS instruction, the OUT, OUTN, SET, RST,
TML, TIM, TMH, or TMS instruction can be programmed.
•
Timedown from the preset value is initiated when the operation result directly before the timer input is on.
•
The timer output turns on when the current value (timed value) reaches 0.
•
The current value returns to the preset value when the timer input is off.
•
Timer preset and current values can be changed using
WindLDR
without transferring the entire program to the CPU
again. From the
WindLDR
menu bar, select Online > Monitor, then select Online > Point Write. To change a timer pre-
set value, specify the timer number with a capital T and a new preset value. If the timer preset value is changed during
timedown, the timer remains unchanged for that cycle. The change will be reflected in the next time cycle. To change a
timer current value, specify the timer number with a small t and a new current value while the timer is in operation. The
change takes effect immediately.
•
If the timer preset value is changed to 0, then the timer stops operation, and the timer output is turned on immediately.
•
If the current value is changed during timedown, the change becomes effective immediately.
Timer Accuracy
Timer accuracy due to software configuration depends on three factors: timer input error, timer counting error, and timeout
output error. These errors are not constant but vary with the user program and other causes.
Timer Input Error
The input status is read at the END processing and stored to the input RAM. So, an error occurs depending on the timing
when the timer input turns on in a scan cycle. The same error occurs on the normal input and the catch input. The timer
input error shown below does not include input delay caused by the hardware.
I1
Ladder Diagram
TIM
D10
T5
Prgm Adrs
Instruction
Data
0
1
2
3
LOD
TIM
OUT
I1
T5
D10
Q0
Program List
Q0
Program Processing
Actual Input
ON
OFF
Input RAM
ON
OFF
Timer Star t
Minimum Error
Tie
END
1 scan time
TIM
END
Tet
Program Processing
Actual Input
ON
OFF
Input RAM
ON
OFF
Timer Star t
Maximum Error
END
1 scan time
TIM
END
Tet
TIM
Tie
When the input turns on immediately before the
END processing, Tie is almost 0. Then the timer
input error is only Tet (behind error) and is at its
minimum.
When the input turns on immediately after the END pro-
cessing, Tie is almost equal to one scan time. Then the
timer input error is Tie + Tet = one scan time + Tet
(behind error) and is at its maximum.
Tie: Time from input turning on to the END processing
Tet: Time from the END processing to the timer instruction execution
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