NAM BOOT.TXT

* VEGAS 6809 BOOTSTRAP

* EQUATES

STACK EQU $C07F
SCTBUF EQU $C300
LECSEC EQU $F812 LECTURE SECTEUR DU MONITEUR
*
* START OF UTILITY
*
 ORG $C100
BOOT BRA LOAD0
 FCB $00,$00,$00		
TRK FCB $00 FILE START TRACK
 FCB $00 FILE START SECTOR
 FCB $00 DENSITY FLAG
TADR FDB $C100 TRANSFER ADDRESS
LADR FDB $0000 LOAD ADDRESS
LOAD0 LDS #STACK SETUP STACK
 LDD >TRK SETUP STARTING TRK & SCT
 STD >SCTBUF 
 LDY #SCTBUF+256
*
* PERFORM ACTUAL BOOT LOAD
*
LOAD1 BSR GETCH GET A CHARACTER
 CMPA #$02 DATA RECORD HEADER?
 BEQ LOAD2 SKIP, IF SO
 CMPA #$16 XFR ADDRESS HEADER?
 BNE LOAD1 LOOP IF NEITHER
 BSR GETCH GET TRANSFER ADDRESS
 STA >TADR
 BSR GETCH
 STA >TADR+1
 BRA LOAD1 CONTINUE LOAD

LOAD2 BSR GETCH GET LOAD ADDRESS
 STA >LADR 
 BSR GETCH
 STA >LADR+1
 BSR GETCH GET BYTE COUNT
 TFR A,B PUT IN B
 TSTA 
 BEQ LOAD1 LOOP IF COUNT = 0
 LDX >LADR GET LOAD ADDRESS

LOAD3 PSHS X,B 
 BSR GETCH GET A DATA CHARACTER
 PULS X,B 
 STA ,X+ PUT CHARACTER
 DECB END OF DATA IN RECORD?
 BNE LOAD3 LOOP IF NOT

 BRA LOAD1 GET ANOTHER RECORD
*
* GET CHARACTER ROUTINE
*
GETCH CMPY #SCTBUF+256 OUT OF DATA?
 BNE GETCH4 GO READ CHARACTER IF NOT
 LDX #SCTBUF POINT TO BUFFER
 LDD ,X GET FORWARD LINK
 BEQ GO  IF ZERO, FILE IS LOADED
 BSR READ READ NEXT SECTOR
 BNE BOOT START OVER IF ERROR
 LDY #SCTBUF+4 POINT PAST LINK
GETCH4 LDA ,Y+ ELSE GET A CHARACTER
 RTS 
*
* FILE IS LOADED, JUMP TO IT
*
GO JMP [TADR]
*
* READ SINGLE SECTOR
*
READ JMP >LECSEC
 RTS
 

 END BOOT