; SCC interrupt handler for IBM-PC include pmacros.h ; variables from C dseg extvar sccvecloc,word extvar sccmaxvec,byte extvar sccpolltab,word ifdef LARGEDATA extvar sccchan,dword else extvar sccchan,word endif dsegend ; variables from pcint.asm dseg extvar sssave,word extvar spsave,word extvar intstk,byte dsegend extproc doret ; sccvec is the interrupt handler for SCC interrupts using INTACK pubproc sccvec cli ; this code is not re-entrant, so make sure it ; is not interrupted. some multi-taskers ; intercept interrupt handlers, so be careful! push ax ; save ax first. push ds ; save on user stack getds mov ds,ax mov sssave@,ss ; stash user stack context mov spsave@,sp mov ss,ax ; set up interrupt stack lea sp,intstk@ push bx ; save user regs on interrupt stack push cx push dx push bp push si push di push es ifndef LARGEDATA mov es,ax ; small data assumes ES == DS endif if TURBO or MSC cld ; in case "movsb" or "movsw" is used endif ; Read SCC interrupt vector and check it sccint: mov dx,sccvecloc@ out dx,al ; Generate INTACK jmp short d1 ; Delay d1: jmp short d2 d2: jmp short d3 d3: in al,dx ; Read the vector cmp al,sccmaxvec@ ; Check for a legal vector jnc clrret ; It should not be >= the maximum ; If it is, ignore the interrupt ; Extract channel number and status from vector. Determine handler address. mov bl,al ; Copy vector (need it later for status) shr bl,1 ; Discard least significant bit jc clrret ; It should not be a 1 and bx,7ch ; Isolate channel number (and make word) xor bl,04h ; Toggle A/B channel bit ifdef LARGEDATA les si,sccchan@[bx] ; Read address of channel structure else shr bl,1 ; Discard another bit mov si,sccchan@[bx] ; Read address of channel structure endif test si,si ; Test for NULL je clrret ; No channel struct, ignore it and ax,06h ; Isolate status info from vector add ax,ax ; Make index in FAR PTR array mov bx,ax ; It must be in BX ; Call the handler (defined in C), with sccchan struct as a parameter pushes push si ; Put channel struct as a parameter ifdef LARGEDATA call dword ptr es:[bx+si] ; Call the handler else call dword ptr [bx+si] ; Call the handler endif pop si ; Get channel struct back popes ; Reset highest priority interrupt ifdef LARGEDATA mov dx,es:16[si] ; Get control register address else mov dx,16[si] ; Get control register address endif mov al,38h ; "Reset Highest IUS" opcode out dx,al ; to WR0 jmp short d4 ; settling delay d4: jmp short d5 d5: ; Determine if more interrupt requests are coming in from the SCCs jmp sccint ; keep trying until no vector returned ; Clear the ISR bit in the PIC and return from interrupt clrret: jmp doret@ ; execute code in pcint.asm pend sccvec ; sccnovec is the interrupt handler for SCC interrupts using polling pubproc sccnovec cli ; this code is not re-entrant, so make sure it ; is not interrupted. some multi-taskers ; intercept interrupt handlers, so be careful! push ax ; save ax first. push ds ; save on user stack getds mov ds,ax mov sssave@,ss ; stash user stack context mov spsave@,sp mov ss,ax ; set up interrupt stack lea sp,intstk@ push bx ; save user regs on interrupt stack push cx push dx push bp push si push di push es ifndef LARGEDATA mov es,ax ; small data assumes ES == DS endif if TURBO or MSC cld ; in case "movsb" or "movsw" is used endif ; Find the SCC generating the interrupt by polling all attached SCCs ; reading RR3A (the interrupt pending register) sccintnv: lea si,sccpolltab@ ; Point to polling table sccpoll: mov dx,[si] ; Get chan A CTRL address inc si inc si test dx,dx ; End of table without finding it je clrret ; Then return from interrupt mov al,3 ; Select RR3A out dx,al jmp short d6 ; Delay d6: jmp short d7 d7: jmp short d8 d8: in al,dx test al,al ; Test if a nonzero IP here jnz sccip ; Yes, handle it inc si ; No, next A CTRL inc si jmp sccpoll ; Read SCC interrupt vector from RR2B, it should always be correct ; Extract channel number and status from vector. Determine handler address. sccip: mov dx,[si] ; Read B CTRL address mov al,2 ; Select RR2B out dx,al jmp short d9 ; Delay d9: jmp short d10 d10: jmp short d11 d11: in al,dx ; Read the vector mov bl,al ; Copy vector (need it later for status) shr bl,1 ; Discard least significant bit and bx,7ch ; Isolate channel number (and make word) xor bl,04h ; Toggle A/B channel bit ifdef LARGEDATA les si,sccchan@[bx] ; Read address of channel structure else shr bl,1 ; Discard another bit (sccchan=words) mov si,sccchan@[bx] ; Read address of channel structure endif test si,si ; Test for NULL je clrret ; No channel struct, ignore it and ax,06h ; Isolate status info from vector add ax,ax ; Make index in FAR PTR array mov bx,ax ; It must be in BX ; Call the handler (defined in C), with sccchan struct as a parameter pushes push si ; Put channel struct as a parameter ifdef LARGEDATA call dword ptr es:[bx+si] ; Call the handler else call dword ptr [bx+si] ; Call the handler endif pop si ; Remove parameter from stack popes ; Check for more interrupt pending bits jmp sccintnv pend sccnovec ; scctvec is called as the replacement timer tick interrupt handler every 55ms. ; it calls scctim() and then jumps to the original handler. ; when the constant SCC_HWTIMER is defined during compilation of SCC.C, ; we'll install it directly on the timer hardware interrupt, not on the ; timer-tick user-exit (int 1c) because some programs take over that one ; without saving and calling the original handler installed there... ; (also, Phil Karn points out the int 1c is sluggish when DoubleDos is running) extproc scctim pubproc scctvec cli ; this code is not re-entrant, so make sure it ; is not interrupted. some multi-taskers ; intercept interrupt handlers, so be careful! push ax ; save ax first. push ds ; save on user stack getds mov ds,ax mov sssave@,ss ; stash user stack context mov spsave@,sp mov ss,ax ; set up interrupt stack lea sp,intstk@ push bx ; save user regs on interrupt stack push cx ; (only those not saved by C) push dx push es ifndef LARGEDATA mov es,ax ; small data assumes ES == DS endif call scctim@ ; call timer tick routine (in C) pop es ; restore everything pop dx pop cx pop bx mov ss,sssave@ mov sp,spsave@ ; restore original stack context pop ds pop ax db 0eah ; opcode for a far jump pubvar sccotvec, ; original INT handler address ; is stored here by initialization code pend scctvec end