C128D floppy drive ROM

From: William Levak (wlevak_at_cyberspace.org)
Date: 2000-01-14 02:14:40

This is the disassembly of the drive ROM reset vector:

The reset vector is EAA0

EAA0  SEI
EAA1  CLD
EAA2  LDX #$66
EAA4  JMP $FF10

FF10  STX $1803
FF13  LDA #$02
FF15  JMP $A65A

A65A  LDA $1860
A65D  BRK

The interrupt vector ist FE67

FE67 JMP($02A9)

At this point, the RAM has not even been cleared, let alone filled with
values.  The drive should crash at this point, but it doesn't.

A65A is the beginning of the chip initialization routine in the 1571.  It
jumps to several locations and then jumps back and finishes the
initialization.

The routine above makes no sense to me.

Does anyone have an explanation??



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