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Entry type: FAQ Entry ID: 12981782, Entry date: 08/18/2008

Which PCI slots in the SIMATIC PCs have exclusive use of the interrupt - i.e. don't share it with other PCI devices?

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Configuration notes:

Overview of PCI slots without interrupt sharing
In the example below we show the assignments of the PCI IRQ lines to the PCI slots of Rack PC 847B. Modules requiring an exclusive interrupt can be used for slot 5 or 8 and 6 or 9 in the APIC mode.

Assigning the exclusive interrupt in the BIOS setup with PIC mode only
The BIOS is set in the as-delivered status so that the interrupts are automatically assigned to the slots when the system starts up. Depending on the system setup, several slots might therefore have the same interrupt assigned to them. This is known as interrupt sharing. No exclusive interrupt is provided in PIC mode. You have to switch off system resources to get exclusive interrupts. You cannot predict which PIC interrupts are assigned by the BIOS on the next startup.

Assignment of the PCI slots in the SIMATIC PC to the interrupts
The table below (Table 03) shows the PCI slots in the SIMATIC PCs that do not share the interrupt with other PCI devices, i.e. use the interrupt exclusively. The following settings must also be defined in WinAC systems with RTX:

PC designation PCI slot no. with exclusive interrupt PCI interrupt line used
Box PC 620
(6ES7647-2.. + 6ES7647-5..)
1 and 2 1(=A)
Box PC 820 2 2(=B)
Box PC 840 2 and 4 2(=B)
Box PC 627B 1 and 2  
Box PC 827B 1 and 2  
Microbox 427B 1 and 2  
RI45PIII 2 or 4 2(=B)
Rack PC 830 2 1(=A)
Rack PC 840 2 or 6*) 2(=B)
Rack PC 847B 5 or 8 and 6 or 9  
FI45 V2 2 2(=B)
Panel PC 670 1 1(=A)
Panel PC 870 2 2(=B)
Panel PC 677 1 and 2 1(=B) and 2(=C)
Panel PC 577B 1 and 2  
Panel PC 477B embedded 1 and 2  
Panel PC 677B 1 and 2  
Power PG 1 1(=A)
PCU50/PCU70 1 1(=A)
Panel PC 877 2 or 4 1(=B) and 2(=C)
Panel PC 870 V2 2 or 4 2 or 4
Table 01: Settings for WinAC systems with RTX
*) PCI slots with no. 2 and 6 share an interrupt in each case. Switching off USB 2.0 makes slot 4 available likewise with an exclusive interrupt.

The hardware wiring is shown here. Note here that the PCI interrupt lines can be divided by settings in the BIOS Setup.
You should therefore also check the following Setup setting in the BIOS: 

  • To enter the BIOS you have to press "F2" while starting the PC.

  • Select the menu item "Advanced" in the menu bar.

  • Select "PCI Configuration"

  • Checking the settings with "PCI IRQ Line" 
    The setting "AUTOSELECT" is normally recommended.

There you can assign an ISA interrupt for the exclusive PCI slot. However, the setting is only taken for non-ACPI operating systems.
This applies exclusively to PCI cards that use only one interrupt line.

Rack PC IL 43:
As a rule, the Rack PC does not support exclusive interrupts. However, if a module requires an exclusive interrupt, it can be assigned by disabling some of the basic functions on the PC board. You can find information about the configuration of the resources in the technical manual for the "D2156-S" motherboard.


  1. PCI slots no. 5+6 are located in front of the PCI bridge and PCI slots no. 1+2 are located behind the PCI bridge of rack PC 840 and 847B.
  2. Panel PC 870 V2 has no exclusive interrupt in the basic function. You must first switch off a number of functions on the motherboard to be able to set an exclusive interrupt.
  3. With Panel PC 877, the exclusive interrupts can only be used if the USB controllers are switched off partly or completely.
  4. The WinAC RTX supports up to 4 CPs. Therefore, we would advise you to choose a computer with a large number of exclusive interrupts.
  5. If there isn't an interrupt available for a CP, the CP operates in polling mode, not in interrupt mode. This can impair the performance of the CP. In this regard, refer to the section on "Optimizing the performance of a DP interface" in the SIMATIC WinAC RTX manual.
  6. For Rack PC 840, only one slot can be used exclusively in each case.
  7. This function can now also be used in ACPI operating systems. The requirement for this is a version of BIOS released as of 10/2002.

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