Siemens Simatic S7-400 - Manual (Page 499)

Interface Submodules
13-3
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Interrupt Assignments
When configuring the interface submodules in the BIOS setup, you can assign ISA
interrupts to the three interrupts of an interface submodule (IRQa, IRQb, IRQc). For
this purpose, enter the ISA interrupt provided in the relevant screen form. See the
table below for the format for entering the interrupt.
Table 13-1 Format of the Interrupt Entry in the BIOS Setup of the Interface Submodule
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
1 1 1 0 ISA interrupt number
If you enter the value “F0
H
” instead of the ISA interrupt (“EX
H
”), this interrupt is
processed via a shared interrupt.
Shared Interrupt
Since the number of interrupts is limited due to AT-compatibility, it is possible to
assign several individual interrupts of the interface submodules to a shared
interrupt. The shared interrupt is shared by all interface submodule interrupts within
an expansion module where the interrupt assignment “F0
H
” has been entered.
The shared interrupt is assigned to the ISA interrupt during configuration of the
interface submodule in the BIOS setup.
Signal Switching
In an EXM 478 expansion module, two interface submodule signals can be
switched to another (signal switching). This signal switching is done during
configuration of the interface submodule in the BIOS setup.
Refer to the interface submodule description to find out if an interface submodule
requires signals from a further interface submodule, that is, if signal switching is
necessary.