P/+DA2

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P/+DA2

This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.

Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.

Tape/disk:	Home » Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_37.ADF
Filename:	P/+DA2
Read OK:	✔
File size:	07DF bytes
Load address:	2B204556
Exec address:	D324144

Duplicates

There is 1 duplicate copy of this file in the archive:

Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_37.ADF » P/+DA2
Personal collection » Acorn hard disk » zipped_disks » elk03 » eug37/P/+DA2

File contents

The result:
2000 PHP
2001 PHA
2002 TXA
2003 PHA
2004 LDX #&00
2006 LDA &2016,X
2009 JSR &FFEE
200C INX
200D CMP #&00
200F BNE &F5
2011 PLA
2012 TAX
2013 PLA
2014 PLP
2015 RTS
2016 EQUS "Hello"
201B EQUW &0D0A
201D EQUB &00 "."

Note that the disassembler does not assign labels or variable names.

The "." after an EQUB is the ASCII code as printed by *DUMP ("." if
<32 or >126), and is provided for password programs when one character
at a time is tested.  The character is also printed following an
opcode using the Immediate addressing mode (i.e. data byte after the
instruction), so that "LDA #&48" and "CMP #&65" demonstrate that the
program under scrutiny loads "H" into the accumulator and compares
the accumulator with "e" respectively.

Of course, using the disassembler requires some knowledge of 6502
machine code, in order that you can discern whether the current byte
is an opcode or a piece of data, and so that you can achieve speed in
disassembly by looking at the program and being able to type OOOOOOOOOO,
knowing that ten opcode instructions are on the screen.

Considering that it used to take me about an hour to disassemble a
256-byte *DUMP listing, the time saving is enormous, and I can now do
about four 256-byte pages in ten minutes.  Theoretically, a whole 16K
ROM could be done in about an hour and a half, though it is better to
split it into sections - it is best to end a section after an RTS or
JMP instruction.

The output file can also grow very fast, at the rate of about 10 bytes
per byte of machine code - decoding a ROM would take 160K of output
files.  I still intend to disassemble the MOS though, so that I can
unravel its mysteries.  I have decoded the part of the MOS which deals
with OSWORDs 14 and 15 - the real-time clock code, and found the
hardwired 1900-century code at &9881 in the Terminal ROM.

The disassembler has enabled hacking to go into warp drive!  Try it and
see for yourself!

Please feel free to request additional features, if they would be useful.

00000000  0d 54 68 65 20 72 65 73  75 6c 74 3a 0d 32 30 30  |.The result:.200|
00000010  30 20 50 48 50 0d 32 30  30 31 20 50 48 41 0d 32  |0 PHP.2001 PHA.2|
00000020  30 30 32 20 54 58 41 0d  32 30 30 33 20 50 48 41  |002 TXA.2003 PHA|
00000030  0d 32 30 30 34 20 4c 44  58 20 23 26 30 30 0d 32  |.2004 LDX #&00.2|
00000040  30 30 36 20 4c 44 41 20  26 32 30 31 36 2c 58 0d  |006 LDA &2016,X.|
00000050  32 30 30 39 20 4a 53 52  20 26 46 46 45 45 0d 32  |2009 JSR &FFEE.2|
00000060  30 30 43 20 49 4e 58 0d  32 30 30 44 20 43 4d 50  |00C INX.200D CMP|
00000070  20 23 26 30 30 0d 32 30  30 46 20 42 4e 45 20 26  | #&00.200F BNE &|
00000080  46 35 0d 32 30 31 31 20  50 4c 41 0d 32 30 31 32  |F5.2011 PLA.2012|
00000090  20 54 41 58 0d 32 30 31  33 20 50 4c 41 0d 32 30  | TAX.2013 PLA.20|
000000a0  31 34 20 50 4c 50 0d 32  30 31 35 20 52 54 53 0d  |14 PLP.2015 RTS.|
000000b0  32 30 31 36 20 45 51 55  53 20 22 48 65 6c 6c 6f  |2016 EQUS "Hello|
000000c0  22 0d 32 30 31 42 20 45  51 55 57 20 26 30 44 30  |".201B EQUW &0D0|
000000d0  41 0d 32 30 31 44 20 45  51 55 42 20 26 30 30 20  |A.201D EQUB &00 |
000000e0  22 2e 22 0d 0d 4e 6f 74  65 20 74 68 61 74 20 74  |"."..Note that t|
000000f0  68 65 20 64 69 73 61 73  73 65 6d 62 6c 65 72 20  |he disassembler |
00000100  64 6f 65 73 20 6e 6f 74  20 61 73 73 69 67 6e 20  |does not assign |
00000110  6c 61 62 65 6c 73 20 6f  72 20 76 61 72 69 61 62  |labels or variab|
00000120  6c 65 20 6e 61 6d 65 73  2e 0d 0d 54 68 65 20 22  |le names...The "|
00000130  2e 22 20 61 66 74 65 72  20 61 6e 20 45 51 55 42  |." after an EQUB|
00000140  20 69 73 20 74 68 65 20  41 53 43 49 49 20 63 6f  | is the ASCII co|
00000150  64 65 20 61 73 20 70 72  69 6e 74 65 64 20 62 79  |de as printed by|
00000160  20 2a 44 55 4d 50 20 28  22 2e 22 20 69 66 0d 3c  | *DUMP ("." if.<|
00000170  33 32 20 6f 72 20 3e 31  32 36 29 2c 20 61 6e 64  |32 or >126), and|
00000180  20 69 73 20 70 72 6f 76  69 64 65 64 20 66 6f 72  | is provided for|
00000190  20 70 61 73 73 77 6f 72  64 20 70 72 6f 67 72 61  | password progra|
000001a0  6d 73 20 77 68 65 6e 20  6f 6e 65 20 63 68 61 72  |ms when one char|
000001b0  61 63 74 65 72 0d 61 74  20 61 20 74 69 6d 65 20  |acter.at a time |
000001c0  69 73 20 74 65 73 74 65  64 2e 20 20 54 68 65 20  |is tested.  The |
000001d0  63 68 61 72 61 63 74 65  72 20 69 73 20 61 6c 73  |character is als|
000001e0  6f 20 70 72 69 6e 74 65  64 20 66 6f 6c 6c 6f 77  |o printed follow|
000001f0  69 6e 67 20 61 6e 0d 6f  70 63 6f 64 65 20 75 73  |ing an.opcode us|
00000200  69 6e 67 20 74 68 65 20  49 6d 6d 65 64 69 61 74  |ing the Immediat|
00000210  65 20 61 64 64 72 65 73  73 69 6e 67 20 6d 6f 64  |e addressing mod|
00000220  65 20 28 69 2e 65 2e 20  64 61 74 61 20 62 79 74  |e (i.e. data byt|
00000230  65 20 61 66 74 65 72 20  74 68 65 0d 69 6e 73 74  |e after the.inst|
00000240  72 75 63 74 69 6f 6e 29  2c 20 73 6f 20 74 68 61  |ruction), so tha|
00000250  74 20 22 4c 44 41 20 23  26 34 38 22 20 61 6e 64  |t "LDA #&48" and|
00000260  20 22 43 4d 50 20 23 26  36 35 22 20 64 65 6d 6f  | "CMP #&65" demo|
00000270  6e 73 74 72 61 74 65 20  74 68 61 74 20 74 68 65  |nstrate that the|
00000280  0d 70 72 6f 67 72 61 6d  20 75 6e 64 65 72 20 73  |.program under s|
00000290  63 72 75 74 69 6e 79 20  6c 6f 61 64 73 20 22 48  |crutiny loads "H|
000002a0  22 20 69 6e 74 6f 20 74  68 65 20 61 63 63 75 6d  |" into the accum|
000002b0  75 6c 61 74 6f 72 20 61  6e 64 20 63 6f 6d 70 61  |ulator and compa|
000002c0  72 65 73 0d 74 68 65 20  61 63 63 75 6d 75 6c 61  |res.the accumula|
000002d0  74 6f 72 20 77 69 74 68  20 22 65 22 20 72 65 73  |tor with "e" res|
000002e0  70 65 63 74 69 76 65 6c  79 2e 0d 0d 4f 66 20 63  |pectively...Of c|
000002f0  6f 75 72 73 65 2c 20 75  73 69 6e 67 20 74 68 65  |ourse, using the|
00000300  20 64 69 73 61 73 73 65  6d 62 6c 65 72 20 72 65  | disassembler re|
00000310  71 75 69 72 65 73 20 73  6f 6d 65 20 6b 6e 6f 77  |quires some know|
00000320  6c 65 64 67 65 20 6f 66  20 36 35 30 32 0d 6d 61  |ledge of 6502.ma|
00000330  63 68 69 6e 65 20 63 6f  64 65 2c 20 69 6e 20 6f  |chine code, in o|
00000340  72 64 65 72 20 74 68 61  74 20 79 6f 75 20 63 61  |rder that you ca|
00000350  6e 20 64 69 73 63 65 72  6e 20 77 68 65 74 68 65  |n discern whethe|
00000360  72 20 74 68 65 20 63 75  72 72 65 6e 74 20 62 79  |r the current by|
00000370  74 65 0d 69 73 20 61 6e  20 6f 70 63 6f 64 65 20  |te.is an opcode |
00000380  6f 72 20 61 20 70 69 65  63 65 20 6f 66 20 64 61  |or a piece of da|
00000390  74 61 2c 20 61 6e 64 20  73 6f 20 74 68 61 74 20  |ta, and so that |
000003a0  79 6f 75 20 63 61 6e 20  61 63 68 69 65 76 65 20  |you can achieve |
000003b0  73 70 65 65 64 20 69 6e  0d 64 69 73 61 73 73 65  |speed in.disasse|
000003c0  6d 62 6c 79 20 62 79 20  6c 6f 6f 6b 69 6e 67 20  |mbly by looking |
000003d0  61 74 20 74 68 65 20 70  72 6f 67 72 61 6d 20 61  |at the program a|
000003e0  6e 64 20 62 65 69 6e 67  20 61 62 6c 65 20 74 6f  |nd being able to|
000003f0  20 74 79 70 65 20 4f 4f  4f 4f 4f 4f 4f 4f 4f 4f  | type OOOOOOOOOO|
00000400  2c 0d 6b 6e 6f 77 69 6e  67 20 74 68 61 74 20 74  |,.knowing that t|
00000410  65 6e 20 6f 70 63 6f 64  65 20 69 6e 73 74 72 75  |en opcode instru|
00000420  63 74 69 6f 6e 73 20 61  72 65 20 6f 6e 20 74 68  |ctions are on th|
00000430  65 20 73 63 72 65 65 6e  2e 0d 0d 43 6f 6e 73 69  |e screen...Consi|
00000440  64 65 72 69 6e 67 20 74  68 61 74 20 69 74 20 75  |dering that it u|
00000450  73 65 64 20 74 6f 20 74  61 6b 65 20 6d 65 20 61  |sed to take me a|
00000460  62 6f 75 74 20 61 6e 20  68 6f 75 72 20 74 6f 20  |bout an hour to |
00000470  64 69 73 61 73 73 65 6d  62 6c 65 20 61 0d 32 35  |disassemble a.25|
00000480  36 2d 62 79 74 65 20 2a  44 55 4d 50 20 6c 69 73  |6-byte *DUMP lis|
00000490  74 69 6e 67 2c 20 74 68  65 20 74 69 6d 65 20 73  |ting, the time s|
000004a0  61 76 69 6e 67 20 69 73  20 65 6e 6f 72 6d 6f 75  |aving is enormou|
000004b0  73 2c 20 61 6e 64 20 49  20 63 61 6e 20 6e 6f 77  |s, and I can now|
000004c0  20 64 6f 0d 61 62 6f 75  74 20 66 6f 75 72 20 32  | do.about four 2|
000004d0  35 36 2d 62 79 74 65 20  70 61 67 65 73 20 69 6e  |56-byte pages in|
000004e0  20 74 65 6e 20 6d 69 6e  75 74 65 73 2e 20 20 54  | ten minutes.  T|
000004f0  68 65 6f 72 65 74 69 63  61 6c 6c 79 2c 20 61 20  |heoretically, a |
00000500  77 68 6f 6c 65 20 31 36  4b 0d 52 4f 4d 20 63 6f  |whole 16K.ROM co|
00000510  75 6c 64 20 62 65 20 64  6f 6e 65 20 69 6e 20 61  |uld be done in a|
00000520  62 6f 75 74 20 61 6e 20  68 6f 75 72 20 61 6e 64  |bout an hour and|
00000530  20 61 20 68 61 6c 66 2c  20 74 68 6f 75 67 68 20  | a half, though |
00000540  69 74 20 69 73 20 62 65  74 74 65 72 20 74 6f 0d  |it is better to.|
00000550  73 70 6c 69 74 20 69 74  20 69 6e 74 6f 20 73 65  |split it into se|
00000560  63 74 69 6f 6e 73 20 2d  20 69 74 20 69 73 20 62  |ctions - it is b|
00000570  65 73 74 20 74 6f 20 65  6e 64 20 61 20 73 65 63  |est to end a sec|
00000580  74 69 6f 6e 20 61 66 74  65 72 20 61 6e 20 52 54  |tion after an RT|
00000590  53 20 6f 72 0d 4a 4d 50  20 69 6e 73 74 72 75 63  |S or.JMP instruc|
000005a0  74 69 6f 6e 2e 0d 0d 54  68 65 20 6f 75 74 70 75  |tion...The outpu|
000005b0  74 20 66 69 6c 65 20 63  61 6e 20 61 6c 73 6f 20  |t file can also |
000005c0  67 72 6f 77 20 76 65 72  79 20 66 61 73 74 2c 20  |grow very fast, |
000005d0  61 74 20 74 68 65 20 72  61 74 65 20 6f 66 20 61  |at the rate of a|
000005e0  62 6f 75 74 20 31 30 20  62 79 74 65 73 0d 70 65  |bout 10 bytes.pe|
000005f0  72 20 62 79 74 65 20 6f  66 20 6d 61 63 68 69 6e  |r byte of machin|
00000600  65 20 63 6f 64 65 20 2d  20 64 65 63 6f 64 69 6e  |e code - decodin|
00000610  67 20 61 20 52 4f 4d 20  77 6f 75 6c 64 20 74 61  |g a ROM would ta|
00000620  6b 65 20 31 36 30 4b 20  6f 66 20 6f 75 74 70 75  |ke 160K of outpu|
00000630  74 0d 66 69 6c 65 73 2e  20 20 49 20 73 74 69 6c  |t.files.  I stil|
00000640  6c 20 69 6e 74 65 6e 64  20 74 6f 20 64 69 73 61  |l intend to disa|
00000650  73 73 65 6d 62 6c 65 20  74 68 65 20 4d 4f 53 20  |ssemble the MOS |
00000660  74 68 6f 75 67 68 2c 20  73 6f 20 74 68 61 74 20  |though, so that |
00000670  49 20 63 61 6e 0d 75 6e  72 61 76 65 6c 20 69 74  |I can.unravel it|
00000680  73 20 6d 79 73 74 65 72  69 65 73 2e 20 20 49 20  |s mysteries.  I |
00000690  68 61 76 65 20 64 65 63  6f 64 65 64 20 74 68 65  |have decoded the|
000006a0  20 70 61 72 74 20 6f 66  20 74 68 65 20 4d 4f 53  | part of the MOS|
000006b0  20 77 68 69 63 68 20 64  65 61 6c 73 0d 77 69 74  | which deals.wit|
000006c0  68 20 4f 53 57 4f 52 44  73 20 31 34 20 61 6e 64  |h OSWORDs 14 and|
000006d0  20 31 35 20 2d 20 74 68  65 20 72 65 61 6c 2d 74  | 15 - the real-t|
000006e0  69 6d 65 20 63 6c 6f 63  6b 20 63 6f 64 65 2c 20  |ime clock code, |
000006f0  61 6e 64 20 66 6f 75 6e  64 20 74 68 65 0d 68 61  |and found the.ha|
00000700  72 64 77 69 72 65 64 20  31 39 30 30 2d 63 65 6e  |rdwired 1900-cen|
00000710  74 75 72 79 20 63 6f 64  65 20 61 74 20 26 39 38  |tury code at &98|
00000720  38 31 20 69 6e 20 74 68  65 20 54 65 72 6d 69 6e  |81 in the Termin|
00000730  61 6c 20 52 4f 4d 2e 0d  0d 54 68 65 20 64 69 73  |al ROM...The dis|
00000740  61 73 73 65 6d 62 6c 65  72 20 68 61 73 20 65 6e  |assembler has en|
00000750  61 62 6c 65 64 20 68 61  63 6b 69 6e 67 20 74 6f  |abled hacking to|
00000760  20 67 6f 20 69 6e 74 6f  20 77 61 72 70 20 64 72  | go into warp dr|
00000770  69 76 65 21 20 20 54 72  79 20 69 74 20 61 6e 64  |ive!  Try it and|
00000780  0d 73 65 65 20 66 6f 72  20 79 6f 75 72 73 65 6c  |.see for yoursel|
00000790  66 21 0d 0d 50 6c 65 61  73 65 20 66 65 65 6c 20  |f!..Please feel |
000007a0  66 72 65 65 20 74 6f 20  72 65 71 75 65 73 74 20  |free to request |
000007b0  61 64 64 69 74 69 6f 6e  61 6c 20 66 65 61 74 75  |additional featu|
000007c0  72 65 73 2c 20 69 66 20  74 68 65 79 20 77 6f 75  |res, if they wou|
000007d0  6c 64 20 62 65 20 75 73  65 66 75 6c 2e 0d 0d     |ld be useful...|
000007df

P/+DA2.m0

P/+DA2.m1

P/+DA2.m2

P/+DA2.m4

P/+DA2.m5

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