Technical data

BIOS and System Programming

CP 486 ⋅ 00/14 VIPA GmbH 67

4.3.5 Interrupt-Management

Interrupt Initiation in the CP

The hardware interrupt IRQ12 (software interrupt 74) on the CP486 can be initiated by

- PLC access to element 1023 of respectively active bank

- BASP activation on back plane bus

The appertaining interrupt vector is filed to address 1D0 - 1D3 (hex). The initiated interrupt must be

reset by accessing the interrupt reset register (address: C000:9F8E) in the interrupt service routine.

Example: Pascal Program for Evaluation of Interrupt 12

PROGRAM INT_74_TEST;

USES CRT, DOS;

CONST EOI : BYTE = $20; { End of Interrupt acknowledgement }

PIC_1 : BYTE = $20; { Address of first Int-Controller }

PIC_2 : BYTE = $A0; { Address of second Int-Controller }

TYPE BITARRAY = ARRAY[0..7] OF BYTE;

VAR OLD_VEC : POINTER;

I : INTEGER;

STATUS,S5_STATUS,CP_STATUS : BYTE;

S5_STATUSBIT,CP_STATUSBIT : BITARRAY;

INT_AKTIVBIT : BOOLEAN;

{$F+}

PROCEDURE INT_74; INTERRUPT; { ***** INTERRUPT - Routine ************}

{$F-}

BEGIN

i:=i+1; { Increase interrupt counter }

INT_AKTIVBIT:=TRUE; { Set flag for the processing }

{ in the main program }

S5_STATUS:=PORT[$281]; { Buffer S5- and CP-register }

CP_STATUS:=PORT[$280];

PORT[PIC_1]:=EOI; { Interrupt acknowledgement to }

PORT[PIC_2]:=EOI; { both interrupt controllers }

END;

PROCEDURE HEX2BIN(STATUS:BYTE;VAR STATUSBIT:BITARRAY); { Conversion HEX --> BIN }

VAR I : INTEGER;

H1 : BYTE;

BEGIN

FOR I:=0 TO 7 DO

BEGIN

H1:=STATUS MOD 2;

IF H1<>0 THEN

STATUSBIT[I]:=1

ELSE

STATUSBIT[I]:=0;

STATUS:=STATUS DIV 2

END;

PROCEDURE FEHLER;