TITLE	"MP6 by Douglas Jones"

; a trap handler to virtualize the hawk 1X 8X instruction
; as the new instruction, MOVEM dst,src ; M[R[dst]] = M[R[src]]

; NOTE:  This code contains general features that are unneeded
; in this example -- parts of the code are designed to be shared
; with other trap handlers -- these are preserved here in order
; to minimize dissonance between this code and the Hawk manual.

	USE	"hawk.h"

STACKSIZE =	16	; a small stack available for local variables
			; inside the trap handler.  Count your local
			; variables carefully and if more are required,
			; enlarge this stack!

; Trap save area, fleshed out from Section 13.3 of the Hawk Manual
; this save area is used only by the illegal instruction trap.

	COMMON	INSSAVEAREA, svSIZE + STACKSIZE

myCODE  =  0 <<2  ; pointer to trap-specific routine entry
myPSW   =  1 <<2  ; initial PSW to use for trap service
svPC    =  2 <<2  ; save area for PC
svR1    =  3 <<2  ; save area for registers
svR2    =  4 <<2
svR3    =  5 <<2
svR4    =  6 <<2
svR5    =  7 <<2
svR6    =  8 <<2
svR7    =  9 <<2
svR8    = 10 <<2
svR9    = 11 <<2
svRA    = 12 <<2
svRB    = 13 <<2
svRC    = 14 <<2
svRD    = 15 <<2
svRE    = 16 <<2
svRF    = 17 <<2
svPSW   = 18 <<2  ; save area for PSW
svMA    = 19 <<2  ; save area for trap MA
svSIZE  = 20 <<2  ; size of register-save area

; initialize myCODE and myPSW fields of save area

LCSAVE	=	.

.	=	INSSAVEAREA + myCODE
	W	INSHANDLER	; the initial PC for the handler
.	=	INSSAVEAREA + myPSW
	W	#00000000	; the initial PSW for the handler

.	=	LCSAVE

	SUBTITLE "trap vector entry"

INSTRTRAP =	#20
LCSAVE	=	.
.	=	INSTRTRAP

; code modified from Section 13.3 of the Hawk manual
        CPUSET  R2,TSV          ; 2 save R2
        LIL     R2,SAVEREGS	; 4 get addr of rest of handler
        JUMPS   R2		; 2 join common code for all traps

.	=	LCSAVE

SAVEREGS:	; enter with R2 pointing to save area and stack
	LIL	R2,INSSAVEAREA	; get save area pointer
	STORE	R1,R2,svR1
	STORE	R3,R2,svR3
	CPUGET	R1,TSV
	CPUGET	R3,TPC
	STORE	R1,R2,svR2
	STORE	R3,R2,svPC
	CPUGET	R1,TMA
	CPUGET	R3,PSW
	STORE	R1,R2,svMA
	STORE	R3,R2,svPSW

        ; straightforward code to save R4-15
	STORE	R4,R2,svR4
	STORE	R5,R2,svR5
	STORE	R6,R2,svR6
	STORE	R7,R2,svR7
	STORE	R8,R2,svR8
	STORE	R9,R2,svR9
	STORE	RA,R2,svRA
	STORE	RB,R2,svRB
	STORE	RC,R2,svRC
	STORE	RD,R2,svRD
	STORE	RE,R2,svRE
	STORE	RF,R2,svRF

	LOAD	R3,R2,myPSW
	LOAD	R1,R2,myCODE
	CPUSET	R3,PSW		; may enable interrupts
	LEA	R3,R2,svPC	; parameter
	ADDI	R2,R2,svSIZE
	JSRS	R1,R1		; call trap service subroutine
	ADDI	R2,R2,-svSIZE

        ; code to restore R4-15
	LOAD 	R4,R2,svR4
	LOAD 	R5,R2,svR5
	LOAD 	R6,R2,svR6
	LOAD 	R7,R2,svR7
	LOAD 	R8,R2,svR8
	LOAD 	R9,R2,svR9
	LOAD 	RA,R2,svRA
	LOAD 	RB,R2,svRB
	LOAD 	RC,R2,svRC
	LOAD 	RD,R2,svRD
	LOAD 	RE,R2,svRE
	LOAD 	RF,R2,svRF

	LOAD	R3,R3,svPSW
	LOAD	R1,R2,svPC
	CPUSET	R3,PSW		; disables interrupts
	CPUSET	R1,TPC
	LOAD	R3,R2,svR3
	LOAD	R1,R2,svR1
	LOAD	R2,R2,svR2
	RTT			; return to user!

	SUBTITLE "Instruction trap service routine"

; activation record, if needed

INSHANDLER:
	; expects: R1 - return address
	;          R2 - activation record pointer, if needed
	;          R3 - pointer to array of saved registers,
	;                 the saved PC is R0, R1-15 are consecutive
	;                 the saved PSW is in word 16 of the array
	;                 the saved memory address is in word 17.
	; must return with R2 unchanged.
	; all other registers may be modified.
	; changes to saved registers will be restored on return from trap.

	; ------- REPLACE THIS LINE WITH YOUR TRAP HANDLER CODE --------
	
	JUMPS	R1		; return

	END