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Routine $0300:   Transfer "general loading loop" & "exit-routines" to C64

This routine primarily transfers the "general loading loop" & "exit-routines"
to the C64. It also reads the final RapidLok sector 3 from Track 18 into the
drive memory and decrypts [$039C-$07FF] (~ RapidLok code routines).


Jump from $0215:

0300: A2 80     LDX #$80
0302: D0 02     BNE $0306

Jump from $030C:

0304: 86 04     STX $04        ; set $80 = Read sector to Job #4 (Track 18 Sector 3)

Jump from $0302, $0309:

0306: 58        CLI            ; enable Interrupts for executing Job #4 (read T18 S3 to [$07xx])
0307: A5 04     LDA $04        ; get Job #4 status/result
0309: 30 FB     BMI $0306

030B: 4A        LSR A          ; A = Job result (=1 if all OK)
030C: D0 F6     BNE $0304      ; branch to restart Job if something wrong with Job result

030E: 78        SEI
030F: 85 24     STA $24        ; [$24]:=0
0311: A2 11     LDX #$11

Jump from $0319:

0313: 95 B5     STA $B5,X      ; [$B5..$C5]:=0 ("M-W" data), [$C6..$C9]=$00,$9B,$36,$CA remains
0315: 9D 08 02  STA $0208,X    ; [$0208..$0218]:=0 ($0206 routine, "M-W" data)
0318: CA        DEX
0319: 10 F8     BPL $0313

031B: A2 01     LDX #$01
031D: A5 C7     LDA $C7
031F: 4A        LSR A
0320: 85 0B     STA $0B
0322: AC 94 02  LDY $0294      ; "Current buffer-index" (e.g. Y=2)

Jump from $032E:

0325: B5 77     LDA $77,X      ; start track & sector ID of file to find & read (encrypted)
0327: 59 17 07  EOR $0717,Y
032A: 95 D6     STA $D6,X      ; [$D6-$D7]:= [$77-$78] xor [$0718-$0719] (if e.g. Y=2)
032C: 88        DEY
032D: CA        DEX
032E: 10 F5     BPL $0325

0330: 29 80     AND #$80
0332: 4A        LSR A
0333: 4A        LSR A
0334: 4A        LSR A
0335: 4D B5 03  EOR $03B5      ; [$03B5] = CLI command at $02DF in $02B6 "exit-routine" (C64)
0338: 8D B5 03  STA $03B5      ; [$03B5]:= [$03B5] xor (([$D7] and #$80) >> 3)
033B: A2 03     LDX #$03
033D: 86 31     STX $31        ; hi address for following file transfer in $0625 routine
033F: E8        INX
0340: A0 9C     LDY #$9C

Jump from $0353, $0358:

0342: B1 05     LDA ($05),Y
0344: 45 C7     EOR $C7
0346: 91 05     STA ($05),Y    ; decrypt [$039C-$07FF]
0348: 66 24     ROR $24
034A: 26 C9     ROL $C9
034C: 26 C8     ROL $C8
034E: 26 C7     ROL $C7
0350: 26 24     ROL $24
0352: C8        INY
0353: D0 ED     BNE $0342

0355: E6 06     INC $06
0357: CA        DEX
0358: 10 E8     BPL $0342

035A: 86 C7     STX $C7        ; [$C7]:=$FF
035C: 86 C8     STX $C8        ; [$C8]:=$FF
035E: 86 C9     STX $C9        ; [$C9]:=$FF
0360: A0 74     LDY #$74
0362: 84 B5     STY $B5
0364: A9 01     LDA #$01
0366: 85 B6     STA $B6        ; [$B5-$B6]:=$0174 (length of "general loading loop" & "exit-routines")
0368: 4A        LSR A

Jump from $0370:

0369: 99 F3 02  STA $02F3,Y    ; [$02F3-$0367]:=0, disable potential hostile patch code there?
036C: 99 2A 02  STA $022A,Y    ; [$022A-$029E]:=0, disable potential hostile patch code there?
036F: 88        DEY
0370: 10 F7     BPL $0369

0372: A0 8C     LDY #$8C       ; defines memory start for file transfer: ($30),Y = $038C
0374: 20 25 06  JSR $0625      ; File transfer: [$B5-$B6] bytes starting at ($30),Y = $038C
0377: A9 08     LDA #$08
0379: 8D 00 18  STA $1800      ; signal for C64-client to exit $0200 transfer-routine
037C: 4C 86 07  JMP $0786

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