coco2: first cut at bootloader

diff --git a/Kernel/platform-coco2/Makefile b/Kernel/platform-coco2/Makefile
index 8ab8fed..7ee229b 100644 (file)
--- a/Kernel/platform-coco2/Makefile
+++ b/Kernel/platform-coco2/Makefile
@@ -45,7 +45,7 @@ $(AOBJS): %$(BINEXT): %.s
 clean:
        rm -f *.o *~
 
-image:
+image: bootfuz.bin
        $(CROSS_LD) -o ../fuzix.bin --map=../fuzix.map --script=fuzix.link \
        crt0.o commonmem.o \
        coco2.o discard.o ../simple.o \
@@ -56,4 +56,8 @@ image:
        ../syscall_proc.o ../syscall_other.o ../mm.o ../swap.o \
        ../tty.o ../devsys.o ../usermem.o ../syscall_fs2.o ../syscall_exec16.o \
        devtty.o libc.o ../vt.o
+# FIXME: need to then convert the decb into an image for the IDE disk booter
+
+bootfuz.bin: bootloader.s
+       lwasm -r -b -obootfuz.bin bootloader.s
 

diff --git a/Kernel/platform-coco2/bootloader.s b/Kernel/platform-coco2/bootloader.s
new file mode 100644 (file)
index 0000000..ea8e524
--- /dev/null
+++ b/Kernel/platform-coco2/bootloader.s
@@ -0,0 +1,145 @@
+sector         equ     0xCFF0
+
+               org 0x600
+
+bootstrap:
+               clr $FFC7               ; Display to 0x200
+               clr $FFC8
+               ldx #0x0200
+wiper:
+               clr ,x+
+               cmpx #0x0400
+               bne wiper
+               pshs cc
+               orcc #$10               ; IRQs off for this lot
+               sta $FFDF               ; 64K mode on
+               ldx #start
+               ldy #0xC000
+copy:                                  ; Move the loader somewhere safe
+               lda ,x+
+               sta ,y+
+               cmpy #end
+               bne copy
+               jmp 0xC000
+               
+;
+;      This code *MUST* remain relocatable
+;
+;      Load IDE blocks 1+ into memory off an LBA drive. With 512 byte
+; sectors we load just under 0xB000 bytes. The first 0x0000-0x8000 bytes are
+; our low memory image. 0x8000-0x8FFF holds the high image (0xF000-0xFFFF) and
+; then the blocks at 0x9000-0xAFFF are used for discard (0x8000-8FFF will be
+; trashed before discard is gone by the exec arguments). Having done the
+; shuffle we then jump in 64K mode to 0x0400 which is our start vector.
+;
+; Important cheat. 256 x 512 is 128K, therefore in LBA mode we never need
+; to touch anything but the low 8bit count for the LBA, the rest we clear
+; and just leave alone.
+;
+start:
+               ldd #'B'*256 + 'O'
+               std 0x0200
+               ldd #'O' * 256 + 'T'
+               std 0x0202
+               ldd #':' * 256 + ' '
+               std 0x0204
+               tfr s,u                 ; Save old stack
+               lds #$FE00              ; Point the stack somewhere clear of
+                                       ; our loading
+               ldx #$0
+               tfr x,y                 ; Load from 0
+
+l0:                                    ; Wait for IDE ready
+               leay -1,y
+               beq timeout
+               lda $FF57
+               bita #0x80
+               bne l0
+               lda #'X'
+               sta 0x0205
+               clr $FF54
+               clr $FF55
+               lda #0x40
+               sta $FF56               ; LBA mode
+               lda #0x01               ; Leave block 0 for MBR etc stuff
+               sta sector
+               ldx #0x0000
+l1:                                    ; Wait busy to clear
+               ldb $FF57
+               leay -1,y
+               beq timeout
+               bitb #0x80
+               bne l1
+
+               sta $FF53               ; sector number to read
+               lda #0x01
+               sta $FF52               ; Some drives clear this each I/O
+               lda #'*'
+               sta 0x0205
+l2:
+               leay -1,y
+               beq timeout
+               lda $FF57
+               bita #0x40              ; Wait DRDY
+               beq l2
+               lda #0x20               ; READ
+               sta $FF57
+l3:
+               leay -1,y
+               beq timeout
+               bita #0x08              ; Wait DRQ
+               beq l3
+               lda #'+'
+               sta 0x0205
+               ldy #0
+               clra
+l4:
+               ldb 0xFF50
+               stb ,x+
+               ldb 0xFF58
+               stb ,x+
+               deca
+               bne l4
+               cmpx #0xB000
+               beq loaded
+               lda #'-'
+               sta 0x0205
+               inc sector
+               lda sector
+               bra l1                  ; Wait busy clear and do next
+timeout:
+               ldb #1                  ; Error 1
+bail:
+               ldx #0
+bail_w:
+               leax 1,x
+               cmpx #0
+               bne bail_w
+               clr $FFC6
+               clr $FFC9               ; Display back where BASIC wants it
+               clra
+               tfr u,s                 ; Recover stack
+               sta $FFDE               ; Back into 32K mode
+               puls cc,pc
+
+diskerr:
+               ldb #2
+               bra bail
+
+loaded:
+               lda #'@'
+               sta 0x0205
+;
+;      We have loaded from 0000 to B000 now relocate bits from 8000-8FFF to
+;      F000-FFFF, 9000-B000 is discard space
+;
+               ldx #0x8000
+               ldy #0xF000
+l5:            ldd ,x++
+               std ,y++
+               cmpy #0xFF00            ; skip last 256 bytes (I/O area)
+               bne l5
+               lda #'.'
+               sta 0x0205
+               jmp 0x0400
+end: