Siemens Simatic S7-400 - Manual (Page 483)

M7-400 Expansions
12-13
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
12.2.2 Interrupt Assignments, Signal Switching EXM 478
Introduction
Up to three interrupts per interface submodule are permitted in an EXM 478
expansion module. The various possible methods of interrupt assignment or
interrupt operation are described below.
Interrupt Assignment
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.
If you enter the value “F0
H
” instead of the ISA interrupt, this interrupt is processed
via a shared interrupt. See below for details.
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 in the EXM 478 expansion modules. 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.
Note
You will find a detailed description of the BIOS setup in the M7-400 application
module or CPU description.