| # | start move.l sp | a5 start the program!
|
|---|
| 1 | move.l #ustk | sp Make space available... |
| 2 | move.l 4(a5) | a5 |
| 3 | move.l $c(a5) | d0 |
| 4 | add.l $14(a5) | d0 |
| 5 | add.l $1c(a5) | d0 |
| 6 | add.l #$100 | d0 |
| 7 | move.l d0 | size |
| 8 | move.l d0 | -(sp) |
| 9 | move.l a5 | -(sp) |
| 10 | move.w d0 | -(sp) |
| 11 | move.w #$4a | -(sp) |
| 12 | trap #1 and free up unused memory |
| 13 | add.l #12 | sp accordingly. |
| 14 | gosuper clr.l -(sp) enter supervisor mode |
| 15 | move.w #32 | -(sp) |
| 16 | trap #1 |
| 17 | addq #6 | sp |
| 18 | move.l d0 | savestk keep track of the old stack |
| 19 | install suba.l a4 | a4 install the reset-program. |
| 20 | move.l #$31415926 | d0 magic number. |
| 21 | move.l d0 | $426(a4) RESVALID |
| 22 | move.l #go | d0 reset program address. |
| 23 | move.l d0 | $42a(a4) RESVECTOR |
| 24 | gouser move.l savestk | -(sp) go back to user mode now |
| 25 | move.w #32 | -(sp) |
| 26 | trap #1 |
| 27 | addq #6 | sp |
| 28 | exit clr.w -(sp) and finish the installation. |
| 29 | move.l size | d0 |
| 30 | move.l d0 | -(sp) |
| 31 | move.w #49 | -(sp) |
| 32 | trap #1 |
| 33 | go sub.l a4 | a4 Start of the reset-program. |
| 34 | move.l #0 | $426(a4) clear the program from memory |
| 35 | move.l #0 | $42a(a4) after a reset! |
| 36 | newbit lea $FFFF8800 | a0 Just replacing $FC0084 of |
| 37 | move.b #$7 | (a0) the ROM here | because we want to |
| 38 | move.b #$C0 | $2(a0) skip over the original version. |
| 39 | move.b #$E | (a0) |
| 40 | move.b #$7 | $2(a0) |
| 41 | move.b $fc001d | d0 |
| 42 | btst #$0 | d0 |
| 43 | beq continue |
| 44 | lea continue(pc) | a6 |
| 45 | move.l #$fc0e1a | a5 |
| 46 | jmp (a5) |
| 47 | continue move.l #$ff820a | a5 Right... the frequency address. |
| 48 | move.b #0 | d0 D0 holds the new frequency. |
| 49 | move.b d0 | (a5) 0 for 60Hz | and 2 for 50Hz. |
| 50 | move.l #$fc00b6 | a6 Continue with original part of |
| 51 | jmp (a6) the ROM... |
| 52 | ds.l 20 Stack space... stack grows |
| 53 | ustk ds.l 1 downwards. |
| 54 | size ds.l 1 Size of memory to keep |
| 55 | savestk ds.l 1 old stack pointer.
|
