; ALTO MESA BOOT LOADER - MBoot.asm ; LOADED ALMOST ANYWHERE AND EXECUTED ; R. Johnsson - 20 Feb 76 ; Last edited January 5, 1980 1:26 PM .TITL BOOT .TXTM B .ENT MBOOT .ENT SwatFlag .SREL MBOOT: BOOT SwatFlag: BREAK .NREL .GET "Mesa-NovaDefs.asm" ;AC0 is pointer to argument list BOOT: DIR ; NO MORE INTERRUPTS MOV 0 2 LDA 0 0,2 ; POINTER TO BOOTMAP RECORD STA 0 PGPTR LDA 0 1,2 STA 0 DCB1+diskaddress LDA 0 2,2 ; initial State STA 0 currentState BLTLOOP: LDA 0 C3 ADD 0 2 LDA 0 0,2 MOV 0 0 SNR JMP DOIT LDA 1 1,2 LDA 3 2,2 BLT ; do some BLTs JMP BLTLOOP C3: 3 DOIT: LDA 3 PGPTR ; POINTER TO BOOTMAP RECORD LDA 0 0,3 ; SN1 STA 0 DCB1+sn1 STA 0 DCB2+sn1 LDA 0 1,3 STA 0 DCB1+sn2 STA 0 DCB2+sn2 LDA 0 5,3 ; first page STA 0 DCB2+pagenumber NEG 0 0 ; -1 COM 0 0 STA 0 DCB1+pagenumber LDA 0 C6 ADD 3 0 STA 0 PGPTR SUB 0 0 ;CLEAR SOME LOCATIONS LDA 2 PAGE1 ; POINTER TO PAGE 1 LOCATIONS STA 0 DISP,2 ;DISPLAY OFF STA 0 IWW,2 ;WAKEUPS WAITING ; JSR .+1 ;RELOCATE CURSOR POINTERS ;CURFIX: LDA 1 POCURSORM1 ; ADD 3 1 ; STA 1 POCURSORM1 ; LDA 1 PMCURSORM1 ; ADD 3 1 ; STA 1 PMCURSORM1 ; ; LDA 0 PCURSORM1 ; LDA 1 PMCURSORM1 ; LDA 3 CN16 ; BLT ;SAVE OLD CURSOR ; LDA 0 PMCURSORM1 ; LDA 1 CUREND ; LDA 3 CN16 ; BLT ;INSERT MESA CURSOR ; NOW FIXUP THE ADDRESSES IN THE DISK BLOCKS JSR .+1 F: MOV 3 1 ; ADDR OF FIXUP TO AC1 LDA 2 DCB2 ; OFFSET OF FIRST DCB IS IN SECOND LDA 3 DCB1 ; AND VICE VERSA ADD 1 2 ADD 1 3 ; THE FIXUPS STA 2 DCB2 STA 3 DCB1 ; NOW FIX THE HEADER AND LABEL ADDRESSES LDA 0 3 2 ADD 1 0 STA 0 3 2 LDA 0 4 2 ADD 1 0 STA 0 4 2 LDA 0 3 3 ADD 1 0 STA 0 3 3 LDA 0 4 3 ADD 1 0 STA 0 4 3 ; START THE DISK AND JUMP INTO LOOP LDA 0 @PGPTR ; pick up first data address STA 0 data 2 ; STORE IT IN DCB STA 2 @PDBLK JMP ADVANCE ; DCB1 AND DCB2 ARE THE DISK CONTROL BLOCKS ; layout of disk command block next = 0 status = 1 command = 2 header = 3 label = 4 data = 5 normalinterrupts = 6 errorinterrupts = 7 unused = 10 diskaddress = 11 ; these hang off the end but are not part of the command prev = 12 blank = 13 numchars = 14 pagenumber = 15 version = 16 sn1 = 17 sn2 = 20 DCB1: DCB2-F ;THIS IS THE FIRST DCB'S LINK WORD 0 ;STATUS 44020 ;COMMAND. READ header and data, check label DHDR-F ;HEADER DCB2+diskaddress-F ;THE LABEL IS READ IN ON TOP OF THE HEADER 0 ;DATA POINTER IS MODIFIED IN OPERATION 0 ;INTERRUPTS ARE INACTIVE 0 0 ;UNUSED 0 ;DISK ADDRESS, ALSO THE FIRST LOCATION FOR OTHER DCB'S LABEL 0 ;prev 0 ;blank 0 ;numchars 0 ;page number 0 ;version 0 ;SN1 0 ;SN2 DCB2: DCB1-F ;THIS IS THE SECOND DCB 0 ;STATUS 44020 ;COMMAND DHDR-F ;HEADER DCB1+diskaddress-F ;LABEL 0 ;DATA 0 0 0 0 ;DISK ADDRESS FOR SECOND DCB, LABEL FOR FIRST DCB 0 ;prev 0 ;blank 0 ;numchars 0 ;page number 0 ;version 0 ;SN1 0 ;SN2 DHDR: .BLK 2 ;read header here CN16: -16. C20: 20 C6: 6 MAXRETRIES: PAGE1: 400 DISP= 420-400 ; display DIW= 421-400 ; display vertical interrupt IWW= 452-400 ; wakeups waiting IACTW= 453-400 ; active interrupts PDBLK: 521 ; disk ERMSK: 367 ; error mask for disk transfer PGPTR: 0 ; pointer to next Page Table entry ;CUREND: 450 ; end of cursor for BLT ;PCURSORM1: 430 ;POCURSORM1: OLDCURSOR-CURFIX-1 ;PMCURSORM1: MESACURSOR-CURFIX-1 ; ;OLDCURSOR: .BLK 20 ; save the entry cursor ;MESACURSOR: ; 104760 ; 154400 ; 124400 ; 104700 ; 104400 ; 104400 ; 104760 ; 000000 ; 003416 ; 004221 ; 004021 ; 003437 ; 000221 ; 004221 ; 003421 ; 000000 ; MAIN LOOP OF THE LOADER. ; ENTER AT ADVANCE WITH AC2= POINTER TO DCB1, AC3= POINTER TO DCB2. ; THE DISK HAS BEEN STARTED on DCB1. ; AT SETUP AC0 HAS ADDRESS FOR NEXT TRANSFER, AC2=POINTER TO ; NEXT DCB, AC3=POINTER TO ACTIVE DCB RETRYCOUNT: 0 SETUP: STA 0 data 2 ; ADDRESS OF NEXT TRANSFER SUB 0 0 STA 0 status 2 ; CLEAR STATUS OF NEXT STA 0 prev,3 ; label of next transfer cleared for check STA 0 blank,3 STA 0 numchars,3 ISZ pagenumber,3 ; bump page number JMP .+1 ISZ pagenumber,3 ; by 2 LDA 0 MAXRETRIES STA 0 RETRYCOUNT RETRY: LDA 1 ERMSK KWAIT: LDA 0 status 3 ; WAIT FOR DISK TO STOP MOV 0 0 SNR JMP KWAIT AND 0 1 SZR ; CHECK FOR ERROR JMP DSKERR ; GOT ONE ; ISZ @CUREND ; COUNT IN CURSOR ; never skip sta 1 diskaddress,3 lda 0 NewDa sta 1 NewDa snz 0 0 ; if changing files jmp ADVANCE sta 0 diskaddress,2 sta 2 @PDBLK sta 2 next,3 lda 0 pagenumber,3 neg 0 0 com 0 0 ; subtract 1 sta 0 pagenumber,2 ; update items for next check lda 1 sn1,3 sta 1 sn1,2 lda 1 sn2,3 sta 1 sn2,2 ADVANCE: MOV 2 0 ; EXCHANGE CURRENT AND INACTIVE DCB POINTERS MOV 3 2 MOV 0 3 ; AC3=POINTER TO ACTIVE DCB LDA 0 0,2 ; CHECK LINK OF DCB JUST FINISHED MOV 0 0 SNR ; TEST FOR LAST PAGE JMP STPR LDA 0 diskaddress,3 ; CURRENT DISK ADDRESS STA 0 @PGPTR ; REPLACE OLD CORE ADDRESS ISZ PGPTR LDA 0 @PGPTR MOVZR 0 0 SZC ; TEST FOR FILE CHANGE JMP ChangeFile MOVZL 0 0 SZR ; test for end of list JMP SETUP ; MORE TO DO STA 0 0 3 ; CLEAR DCB CHAIN LINK JMP SETUP C2: 2 NewDa: 0 ChangeFile: ; AC0 has new file page number lda 1 C2 sub 1 0 sta 0 pagenumber,3 ; new page-2 number to label isz PGPTR sub 0 0 sta 0 next,3 ; break the chain sta 0 sn1,3 sta 0 sn2,3 ; zero the serial number lda 0 @PGPTR sta 0 NewDa ; new disk address isz PGPTR lda 0 @PGPTR ; first memory address for new file jmp SETUP STPR: ; LDA 0 POCURSORM1 ; LDA 1 CUREND ; LDA 3 CN16 ; BLT ; RESTORE CURSOR BREAK: JMP .+1 ; set to swat break (#77400) to break before starting Mesa JMP Emulate ; Here on disk error; status in 0 DSKERR: LDA 1 C20 AND 0 1 SNR ; retry datalate without counting DSZ RETRYCOUNT JMP TryAgain JSR DSKERR1 .TXT "Disk error loading image file" DSKERR1: MOV 3 1 callSwatTrap jmp .-1 TryAgain: SUB 0 0 STA 0 1,3 ;clear active status STA 3 @PDBLK ;restart disk JMP RETRY JMP BOOT+200 ; Error if code too big ; MoveBlock is copied from BfsMl.asm. ; It is not a part of the loader. .ent MoveBlock .srel MoveBlock: .MoveBlock .nrel savedPC = 1 extraArguments = 3 .MoveBlock: sta 3 savedPC,2 mkone 3 3 sub 3 1 sub 0 3 mov 1 0 neg 3 1 lda 3 extraArguments,2 add 3 1 neg 3 3 blt lda 3 savedPC,2 jmp 1,3 .END;