From f6177726d0facab284a8cff27b91b70d48ca8f2f Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Thu, 18 Dec 2014 00:53:20 +0000
Subject: [PATCH] trs80load: TRS80 loader

Assumes single sided double density disk. Sets up the memory map, moves itself
to 0x00-0xff and then loads the kernel at 0x100 before running it.
---
 Kernel/platform-trs80/trs80load.s | 142 ++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 Kernel/platform-trs80/trs80load.s

diff --git a/Kernel/platform-trs80/trs80load.s b/Kernel/platform-trs80/trs80load.s
new file mode 100644
index 00000000..5df52fc9
--- /dev/null
+++ b/Kernel/platform-trs80/trs80load.s
@@ -0,0 +1,142 @@
+;
+;	TRS80 bootblock (256 bytes)
+;
+	    .org 0x0
+start:
+	    ld a, 0x36			; kernel map, 80 column
+	    out (0x84), a
+	    ld a, 0x50			; 80 column, sound, altchars off,
+					; ext I/O on , 4MHz
+	    out (0xEC), a
+	    ld hl, 0x4300
+	    ld de, 0x0
+	    ld bc, 256
+	    ldir
+	    jp go
+;
+;	Assume the boot ROM left us on track 0 and motor on
+;
+floppy_read:
+	    ld bc, 0x81F4		; select drive
+	    out (c), b
+	    out (0xF2), a		; sector please
+	    ld a, 0x80			; READ
+	    out (0xF0), a
+	    ld b, 100
+l1:	    djnz l1
+	    ld de, 0x8116
+	    ld bc, 0xF3
+flopin:	    in a, (0xF0)
+	    and e
+	    jr z, flopin
+	    ini
+	    ld a, d
+flopind:
+	    out (0xF4), a
+	    ini
+	    jr nz, flopind
+flopstat:
+	    in a, (0xF0)
+	    and 0x19
+	    bit 0, a
+	    jr nz, flopstat
+	    or a
+	    ret z
+	    ld de, 0xF850
+	    call prints
+	    .db 'Read',0
+fail:	    jr fail
+
+go:   
+	    ld sp, floppy_read
+
+            ; load the 6845 parameters
+	    ld hl, _ctc6845
+	    ld bc, 1588
+ctcloop:    out (c), b			; register
+	    ld a, (hl)
+	    out (0x89), a		; data
+	    inc hl
+	    djnz ctcloop
+
+   	    ; clear screen
+	    ld hl, 0xF800
+	    inc hl
+	    ld de, 0xF801
+	    ld bc, 1999
+	    ld (hl), ' '
+	    ldir
+	    ld de, 0xF800
+	    call prints
+	    .db 'TRS80Load 0.1',0
+
+	    ld hl, 0x0100
+
+
+
+lastsec:    ld a, (tracknum)
+	    inc a
+	    ld (tracknum), a
+	    cp 40
+	    jr z, booted
+	    out (0xF3), a
+	    ld a, 0x18			; seek
+	    out (0xF0), a
+	    ld b, 100
+cmd1:	    djnz cmd1
+cmdwait:    in a, (0xF0)
+	    bit 0, a
+	    jr z, seekstat
+	    bit 7, a
+	    jr z, cmdwait
+seekstat:
+	    in a, (0xF0)
+	    and 0x18
+	    bit 0, a
+	    jr nz, seekstat
+	    or a
+	    jr z, secmove
+	    ld de, 0xF850
+	    call prints
+	    .db 'seek',0
+bad:	    jr bad
+secmove:    xor a
+	    ld (secnum), a
+nextsec:
+	    ld a, (secnum)
+	    inc a
+	    ld (secnum), a
+	    cp 11
+	    jr z, lastsec
+	    push hl
+	    call floppy_read
+	    pop hl
+	    inc h
+	    jr nextsec
+
+tracknum:   .db 28			; tracks 29-39 (50688 bytes)
+
+
+_ctc6845:				; registers in reverse order
+	    .db 99, 80, 85, 10, 25, 4, 24, 24, 0, 9, 101, 9, 0, 0, 0
+; recycle last crc value as secnum so we fit 256 bytes
+secnum:	    .db 0
+
+
+prints:
+	   pop hl
+printsl:
+	   ld a, (hl)
+	   inc hl
+	   or a
+	   jr z, out
+	   ld (de), a
+	   inc de
+	   jr printsl
+out:	   jp (hl)
+
+booted:	    ld de, 0xF850
+	    call prints
+	    .db 'Booting..',0
+
+; OS starts on the following byte
-- 
2.34.1