Microprocessor Simulator 0 Help
Example - 10swint.asm Software Interrupts
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sms32v50 (3), sms32v50 (6)
Example - 10swint.asm
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; -------------------------------------------------------------- ; An example of software interrupts. ; -------------------------------------------------------------- JMP Start ; Jump past table of interrupt vectors DB 51 ; Vector at 02 pointing to address 51 DB 71 ; Vector at 03 pointing to address 71 Start:
INT 02 ; Do interrupt 02 INT 03 ; Do interrupt 03 JMP Start ; -------------------------------------------------------------- ORG 50 DB E0 ; Data byte - could be a whole table here ; Interrupt code starts here MOV AL,[50] ; Copy bits from RAM into AL NOT AL ; Invert the bits in AL MOV [50],AL ; Copy inverted bits back to RAM OUT 01 ; Send data to traffic lights IRET
; -------------------------------------------------------------- ORG 70
DB 0 ; Data byte - could be a table here ; Interrupt code starts here MOV AL,[70] ; Copy bits from RAM into AL NOT AL ; Invert the bits in AL AND AL,FE ; Force right most bit to zero MOV [70],AL ; Copy inverted bits back to RAM OUT 02 ; Send data to seven segment display IRET ; -------------------------------------------------------------- END ; -------------------------------------------------------------- TASK 26) Write a new interrupt 02 that fetches a key press from the keyboard and stores it into RAM. The IBM PC allocates 16 bytes for key press storage. The 16 locations are used in a circular fashion. 27) Create a new interrupt that puts characters onto the next free screen location. See if you can get correct behaviour in response to the Enter key being pressed (fairly easy) and if the Back Space key is pressed (harder). |
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