mirror of
https://github.com/rzzzwilson/pymlac.git
synced 2025-06-10 09:32:41 +00:00
83 lines
2.6 KiB
NASM
83 lines
2.6 KiB
NASM
;-----------------------
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; 'lc16sd' blockloader code
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; disassembled from munch.ptp
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;-----------------------
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ORG 03700 ; addr code
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ldaddr RCF ; 03700 0001032
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numwrd JMS . ; 03701 0037701 get address of 'chksum' into 'numwrd'
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chksum LAC numwrd ; 03702 0063701 are we are running in high memory (017700+)
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SAM himem ; 03703 0077775
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JMP rdblk ; 03704 0013710 if not, just load tape
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LWC 012 ; 03705 0104012 else turn on the display
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DLA ; 03706 0001003
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DON ; 03707 0003100
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rdblk CAL ; 03710 0100011 initialize block checksum
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DAC chksum ; 03711 0023702
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JMS rdword ; 03712 0037746 get load address
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DAC ldaddr ; 03713 0023700
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ASP ; 03714 0002002 if high bit set
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JMP ldend ; 03715 0013740 then end of tape load
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JMS rdword ; 03716 0037746 else get number of words in block
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DAC numwrd ; 03717 0023701
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JMS rdword ; 03720 0037746 read checksum word, add to checksum
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blklp JMS rdword ; 03721 0037746 get data word
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DAC *ldaddr ; 03722 0123700 store into memory
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LAC ldaddr ; 03723 0063700 get load address
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SAR 3 ; 03724 0003063 echo load address in display (if running)
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AND low10 ; 03725 0047765
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IOR dlya0 ; 03726 0053764
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DAC disp ; 03727 0023766
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LAC *ldaddr ; 03730 0163700 get last data word
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ISZ ldaddr ; 03731 0033700 move 'load address' pointer
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ISZ numwrd ; 03732 0033701 check end of block
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JMP blklp ; 03733 0013721 jump if not ended
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ADD chksum ; 03734 0067702 block end, check checksum
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ASZ ; 03735 0002001 if checksum invalid,
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JMP . ; 03736 0013736 busy wait here
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JMP rdblk ; 03737 0013710 else go get next block
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; end of load, AC is load address, high bit set
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ldend DOF ; 03740 0001012 turn off the display
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IAC ; 03741 0100004
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ASN ; 03742 0102001 if address is 0177777
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HLT ; 03743 0000000 then just halt
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JMS rdword ; 03744 0037746 else get AC contents
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JMP *ldaddr ; 03745 0113700 and jump to start address
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; read a word from tape, leave in AC
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rdword DATA 0 ; 03746 0000000
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ADD chksum ; 03747 0067702
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DAC chksum ; 03750 0023702
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CAL ; 03751 0100011
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RSF ; 03752 0002040
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JMP .-1 ; 03753 0013752
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RRC ; 03754 0001033
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RAL 3 ; 03755 0003003
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RAL 3 ; 03756 0003003
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RAL 2 ; 03757 0003002
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RSF ; 03760 0002040
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JMP .-1 ; 03761 0013760
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RRC ; 03762 0001033
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JMP *rdword ; 03763 0113746
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dlya0 DLYA 0 ; 03764 0020000
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low10 DATA 001777 ; 03765 0001777
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; display routine, used if running in extended memory
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disp DLYA 00000 ; 03766 0020000
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DLXA 00000 ; 03767 0010000
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DSTS 1 ; 03770 0004005
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data 0046000 ;DLVH 02000 ; 03771 0046000
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DLYA 01777 ; 03772 0021777
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DHLT ; 03773 0000000
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DATA 0067766 ; 03774 0067766
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himem DATA 0017702 ; 03775 0017702
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DATA 0010000 ; 03776 0010000
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DATA 0177777 ; 03777 0177777
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DATA 0000000 ; 04000 0000000
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END ;
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