Interrupt Requests Are Not Properly Sent To The Cpu Module - Mitsubishi Electric MELSEC-L Series LD40PD01 User Manual

■Pulse shaping method
As one of measures against external noise or waveform distortion, the following describes the shaping method of a pulse
waveform with dummy resistors.
An effective method for pulse shaping is to apply dummy resistors of several hundreds ohms (/several watts) across pulse
input terminals connected to an encoder to increase a load current through the cables. This method becomes more effective
as the load current value increases.
With this shaping method, the following effects can be obtained.
• When the wiring distance between an encoder and the flexible high-speed I/O control module is long, this shaping method
improves the waveform distortion and the pulse waveform becomes stable.
• When the pulse waveform is unstable due to noise such as external noise, this shaping method stabilizes the pulse
waveform and the noise effects can be reduced.
Ex.
The following figure shows a connection example of dummy resistors at 24VDC.
Flexible high-speed I/O control module
IN 0
(24V input)
240Ω
820Ω
IN 1
(24V input)
240Ω
820Ω
The following example describes how to select a dummy resistor (how to calculate a resistance constant and rated power of a
dummy resistor).
Target
Resistance constant of a dummy resistor (at 24VDC input)
Rated power of a dummy resistor (at 24VDC input)
As a result of the above calculations, apply dummy resistors of 680Ω (/2W) across pulse input terminals in this case.

Interrupt requests are not properly sent to the CPU module

Check item
Is a link to the SI device terminal in the hardware logic correct?
Is the coincidence detection disabled because the addition mode has been
applied?
Is the intelligent function module interrupt pointer setting of the PLC parameter
correct?
IN 0_DIF
B18
IN 0_5V
A19
IN 0_24V
B19
270Ω 4.1kΩ
IN 0_COM
A18
IN 1_DIF
B16
IN 1_5V
A17
IN 1_24V
B17
270Ω 4.1kΩ
IN 1_COM
A16
Install a dummy resistor of hundreds
of ohms (/a few watts) between pulse
input terminals (24V-COM).
Shielded twisted pair cable
Calculation method
Calculate a resistance constant (R) as follows.
• R = V ÷ I = 24V ÷ 35mA = 680Ω
Calculate the power (P1) as follows.
• P1 = V × I = 24V × 35mA = 0.84W (Approx. 1W)
Calculate the power (P2) including margins from the power (P1).
• P2 = P1 × 2 = 0.84 × 2 = 1.68W (Approx. 2W)
Action
Check the block layout and links between blocks in the hardware logic and
make necessary corrections.
To use the coincidence detection interrupt and addition mode together, preset
the value used for the coincidence detection.
Review the intelligent function module interrupt pointer setting.
14.5 Troubleshooting by Symptom
24V
OUT
24V
OUT
E
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