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Routine $0400:   Exit routine (memory clean-up & init 1541)

This routine has two purposes. It gets called from various locations
when a timer runs out or an error occurs: it passes execution to the $07D5
clean up which modifies the $0400 JMP into a dummy BIT command and setting
a Job to execute the modified $0400 exit routine (finishing the clean up).


Jump from $041B, $0420, $D0-Execute Job #1 from $058A, $0627, $0752:

0400: 4C D5 07  JMP $07D5       ; $07D5 is RapidLok's clean-up routine (reset memory and 1541)
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$D0-Execute Job #1 from $07F6:

0400: 2C D5 07  BIT $07D5       ; JMP changed to dummy BIT at $07FA (end of RapidLok's clean-up routine)
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0403: A9 C6     LDA #$C6
0405: 8D 00 1C  STA $1C00       ; $C6=11000110b: Bit rate "10 = 285714 Bit/s", Drive LED on, Drive Motor on
0408: 46 01     LSR $01
040A: E6 3E     INC $3E
040C: 20 05 D0  JSR $D005       ; 1541 ROM: Perform [I] - Initalise command
040F: A2 45     LDX #$45
0411: 9A        TXS
0412: 4C C5 EB  JMP $EBC5       ; 1541 ROM: Power-up RESET routine

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