sam: correct the boot.s code

At this point we seem to be able to load our image. Not yet tried debugging
what happens after bootstrap loads.

diff --git a/Kernel/platform-sam/boot.s b/Kernel/platform-sam/boot.s
index 140b448..02a3e31 100644 (file)
--- a/Kernel/platform-sam/boot.s
+++ b/Kernel/platform-sam/boot.s
@@ -1,7 +1,5 @@
 ;
-;      Boot block, loaded at 0x4000 in the top bank that is free (varies)
-;
-;      Banks and SP we need to double check are ROM0/1/2/3 and valid
+;      Boot block, loaded at 0x8000 in the top bank that is free (varies)
 ;
 ;      The boot block is trivial but it gets a bit fun once we've loaded
 ;      our 14 tracks
@@ -20,10 +18,10 @@
 ;      (or maybe it'll be saner to use 4/5 for kernel 2/3 video..)
 ;
        .area BOOT(ABS)
-       .org 0x4000
+       .org 0x0000
 
 HIMEM  .equ    251
-
+LOMEM  .equ    250
 STATUS .equ    224
 CMD    .equ    224
 TRACK  .equ    225
@@ -33,9 +31,18 @@ DATA .equ    227
 CMD_READ .equ  0x80
 CMD_STEPIN .equ 0x58
 
-       .db 0,0,0,0,0,0,0,0     ; need to work out what goes here
+       .db 0,0,0,0,0,0,0,0,0,0 ; need to work out what goes here
 boot:
        di
+       ; Move ourself from 0x8000 to 0x0000
+       in a,(HIMEM)
+       and #0x1F
+       or #0x20
+       out (LOMEM),a
+       ; Now move to the low mem copy
+       jp go
+go:
+       ld sp,#go
        ld de,#0x0401           ; track 4 sector 2 (we are sector 1)
        ld a,e                  ; Start in bank 2
        ld hl,#0x8000           ; Which we map high
@@ -91,13 +98,13 @@ wait:       in a,(STATUS)           ; Wait for DRQ
        jp z, 0x8000
        ld a,#CMD_STEPIN
        out (CMD),a
-nap2:  ld b,#20
-       djnz nap2
+       ld b,#20
+nap2:  djnz nap2
 wait2: in a,(STATUS)
        bit 0,a
        jr nz,wait2
        jr next_sec
 
-       .org 0x4100
+       .org 0x0100
        .ascii 'BOO'
        .byte 'T'+0x80