Siemens SIMATIC PG 720, Manual

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8
8-5
PG 720 Programming Device
C79000-G7076-C720-02
8.2 Interrupt Assignments
The PG 720 uses the two integrated interrupt controllers of type 82C59 to handle
the 16 hardware interrupts (IRQ 0 to IRQ 15).
The INT output of the slave controller is connected to the IRQ 2 input of the
master controller. Interrupt 9 (IRQ 9) can be used on the bus for the assigned
interrupt 2 (IRQ 2).
In the initialization phase, IRQ is assigned to the software interrupt vector 0A
H (IRQ 2) by the ROM-BIOS.
The priority of the interrupts is in the reverse order of their numbering. This
means the following:
S
Interrupt IRQ 0 has the highest priority and interrupt IRQ 7 the lowest.
S
For triggering IRQ 2, interrupt IRQ 8 has the highest and IRQ 15 the lowest
priority. Interrupts IRQ 8 to IRQ 15 therefore have higher priority than
interrupts IRQ 3 to IRQ 7.
S
The interrupt vectors are initialized and masked when the PG 720 is powered
up.
The following table provides you with an overview of the hardware
interrupts.
Table 8-3 I/O Addresses of the Interrupt Controllers
List of Hardware Interrupts Assigned Interrupt
Vector, Memory
Address
SMI System management interrupt, cannot be masked –
NMI RAM parity; I/O channel parity INT 2 H
IRQ 0 Timer output 0, I/O controller (ISP), internal INT 8 H
IRQ 1 Keyboard (output buffer full) INT 9 H
IRQ 2 Interrupt from slave interrupt controller INT A H
IRQ 3 Serial port (COM 2) INT B H
IRQ 4 V.24/V.28 interface, serial port (COM 1) INT C H
IRQ 5 Parallel port 2 (LPT 2)/MPI INT D H
IRQ 6 Floppy disk INT E H
IRQ 7 Parallel port printer 1 (LPT 1) INT F H
IRQ 8 Real-time clock (RTC) low active INT 70 H
IRQ 9 Software interrupt re-routed to 0AH (IRQ2) (VGA) INT 71 H
IRQ 10 *) INT 72 H
IRQ 11 *) INT 73 H
IRQ 12 Trackball or PS/2 mouse INT 74 H
IRQ 13 Numeric processor INT 75 H
IRQ 14 Winchester; IDE interface INT 76 H
IRQ 15 INT 77 H
*) Depending on the PCMCIA driver, one or two interrupts may be assigned.
Interrupt
Assignment
Priority
I/O Addresses of
the Interrupt
Controllers
Hardware Information