Saia-Burgess Controls AG
Hardware manual for PCD3 series │ Document 26-789 ENG19│ 2018-06-29
Connections on orange terminal block
PCD3.Mxxx0 Classic CPU and expansion enclosure
3-39
3
3.15.2
Interrupt inputs
5540
Saia PCD3.M
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CD3
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CD3
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CD3
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CD3
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CD3
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CD3
Terminal 3 and 4 for interrupts inputs Int0 and Int1
Basics
The digital input modules are not suitable for immediate reaction to events or fast
counting because of the input filters and the influence of the cycle time of the user
program. Most CPUs have 24 VDC interrupt inputs for this purpose.
Two interrupt inputs are located on the main PCB and can be connected via the
8-pin, pluggable terminal block (terminals 3 and 4). Source operation is used.
Interrupt
inputs
Called XOB on
positive edge
Plug
terminal
Direct input query
Base and
standard CPU
Power CPU
PCD3.Mxx60
INT0
XOB 20
3
I 8100
---*
INT1
XOB 21
4
I 8101
---*
* available via media mapping in the device configurator
An associated XOB is called (e.g. XOB 20) on a positive edge on the interrupt
input. The code in this XOB determines how the event responds, e.g. by
incrementing a counter.
The code in XOBs, which are called by interrupt inputs, must be kept as short as
possible so that sufficient time remains between the interrupts to process the rest
of the user program.
Many FBoxes are intended for cyclic calling and are therefore not or only partially
suitable for use in XOBs.
Exception: The FBoxes of the Graftec family (standard library) are well suited.