intcode.inc

MMURTL(tm) Computer Operating System Ver x0.8, source code.

;   MMURTL Operating System Source Code
;   Copyright 1991,1992,1993, Richard A. Burgess
;   ALL RIGHTS RESERVED
;   Version x0.8

;The following calls support ISR operations:
;
; SetIRQVector(IRQnum, pVector)
; GetIRQVector(IRQnum, pVectorRet)
; EndOfIRQ(IRQnum)
; MaskIRQ(IRQnum)
; UnMaskIQR(IRQnum)
;
; In each case, IRQnum is the hardware interrupt request number for the
; IRQ served. This will be 0-7 for interrupts on 8259 #1 and 8-15 for
; interrupts on 8259 #2.  The predetermined IRQ uses are:
;
;	IRQ 0	8254 Timer
;	IRQ 1 	Keyboard (8042)
;	IRQ 2	Cascade from PICU2 (handled internally)
;	IRQ 3 	COMM 2 Serial port
;	IRQ 4	COMM 1 Serial port
;	IRQ 5	Line Printer 2
;	IRQ 6	Floppy disk controller
;	IRQ 7	Line Printer 1
;
;	IRQ 8	CMOS Clock
;	IRQ 9	?
;	IRQ 10	?
;	IRQ 11	?
;	IRQ 12	?
;	IRQ 13	Math coprocessor
;	IRQ 14	Hard disk controller
;	IRQ 15	?

;=============================================================================
;
; SetIntVector(IRQNum, pISR)
; This sets a 32 bit offset for an interrupt handler
; that services one of the hardware interrupts. (0-15)
; The ISR MUST reside in the OS Code segment. This means that only
; device drivers or the OS can set and service interrupts!!
; The DPL is set to 3 (all code can be hardware interrupted).
;
_SetIRQVector PROC FAR
		PUSH EBP
		MOV EBP, ESP
		MOV ECX, [EBP+16]		;Get IRQ number (0-15)
		AND ECX, 0Fh			;0 to 15 max!
		ADD ECX, 20h			;INT number is set for IRQ
		MOV EAX, 08E00h			;Int gate description
		MOV EBX, OSCodeSel		;
		MOV ESI, [EBP+12]		;
		CALL FAR PTR _AddIDTGate ;
		MOV ESP,EBP
		POP EBP
		RETF 8                   ;
_SetIRQVector ENDP
;=============================================================================
;
; GetIntVector(IRQNum, pVectorRet)
; This returns the vector (offset) of the ISR that is currently
; serving the IRQ.
;
_GetIRQVector PROC FAR
		PUSH EBP
		MOV EBP, ESP
		MOV ESP,EBP
		POP EBP
		RETF 8                   ;
_GetIRQVector ENDP

;=============================================================================
;
; Sends End Of Interrupt to PICU (or Both) based on IRQ number (0-15)
; If IRQnum is 0-7 then we send to 1, else we send to 1 then 2.
;
_EndOfIRQ PROC FAR
		PUSH EBP
		MOV EBP, ESP
		PUSH EAX				;
		MOV EAX, [EBP+0Ch]		;Get IRQ number (0-15)
		MOV AH, AL
		MOV AL,20h              ;
		OUT PICU1,AL            ;
		CMP AH, 7				;PICU1 only?
		JBE	EOI00				;Yes
		OUT PICU2,AL            ;Send to 2 also
EOI00:
		POP EAX                 ;
		MOV ESP,EBP
		POP EBP
		RETF 4                  ;
_EndOfIRQ ENDP

;===============================================
; MaskIRQ(IRQnum)  masks the IRQ number specified (0-15).
; The proper PICU is selected based on the IRQ number.
;
_MaskIRQ PROC FAR
		PUSH EBP
		MOV EBP, ESP
		PUSHFD
		CLI
		PUSH EAX				;
		PUSH ECX
		MOV EAX, 1
		MOV ECX, [EBP+0Ch]		;Get IRQ number (0-15)
		AND ECX, 0Fh			;(0-15)
		SHL EAX, CL				;Set the bit for the IRQ (0-7) or (8-15)
		AND AL,AL
		JZ MIRQ2
		MOV AH,AL
		IN AL, PICU1+1
		jmp $+2
		jmp $+2
		OR AL, AH
		OUT PICU1+1, AL
		JMP SHORT MIRQEnd
MIRQ2:
		IN AL, PICU2+1			;AH already has correct value
		jmp $+2
		jmp $+2
		OR AL, AH
		OUT PICU2+1, AL
MIRQEnd:
		POP ECX                 ;
		POP EAX                 ;
		POPFD					;Give em their flags back
		MOV ESP,EBP
		POP EBP
		RETF 4                  ;
_MaskIRQ ENDP
;===============================================
; UnMaskIRQ(IRQnum)  UNmasks the IRQ number specified (0-15).
; The proper PICU is selected based on the IRQ number.
;
_UnMaskIRQ PROC FAR
		PUSH EBP
		MOV EBP, ESP
		PUSHFD
		CLI						;Previous state is reset on POPFD
		PUSH EAX				;
		PUSH ECX
		MOV EAX,1
		MOV ECX,[EBP+0Ch]		;Get IRQ number (0-15)
		AND ECX, 0Fh			; (0-15 only)
		SHL EAX, CL				;Set the bit for the IRQ (0-7)
		AND AL,AL
		JZ UMIRQ2
		MOV AH, AL
		IN AL, PICU1+1
		jmp $+2
		jmp $+2
		NOT AH
		AND AL, AH
		OUT PICU1+1, AL
		JMP SHORT UMIRQEnd
UMIRQ2:
		IN AL, PICU2+1
		jmp $+2
		jmp $+2
		NOT AH
		AND AL, AH
		OUT PICU2+1, AL
UMIRQEnd:
		POP ECX                 ;
		POP EAX                 ;
		POPFD
		MOV ESP,EBP
		POP EBP
		RETF 4                  ;
_UnMaskIRQ ENDP
;
;===============================================