Added main memory BRK handler for GS.

auxmem.misc.s

@@ -179,6 +179,10 @@ IRQBRKRET
             PLA
 NULLRTI     RTI
 
+* Invoked from GSBRK in main memory. On IIgs only.
+GSBRKAUX    >>>   ENTAUX
+            JMP   IRQBRKHDLR     ; See if this works!!
+
 PRERR       LDY   #$01
 PRERRLP     LDA   (FAULT),Y
             BEQ   PRERR1

loader.s

@@ -96,6 +96,11 @@ START       JSR   ROMMENU
             EOR   #$A5             ; Checksum
             STA   RSTV+2
 
+            LDA   #<GSBRK          ; Set BRK vector in main mem
+            STA   $3F0
+            LDA   #>GSBRK
+            STA   $3F0+1
+
             TSX                    ; Save SP at $0100 in aux
             STA   $C005            ; Write to aux
             STX   $0100

mainmem.s

@@ -13,6 +13,9 @@ A2IRQ       >>>   ENTMAIN
 A2IRQ2      PHP                      ; Fake things to look like IRQ
             JMP   (A2IRQV)           ; Call Apple II ProDOS ISR
 
+* BRK handler in main memory. Used on Apple IIgs only.
+GSBRK       >>>   XF2AUX,GSBRKAUX
+
 * Set prefix if not already set
 SETPRFX     LDA   #GPFXCMD
             STA   :OPC7              ; Initialize cmd byte to $C7