--- /dev/null
+********************************************************************
+* dwload implementation for Dragon
+*
+* Copyright 2014-2015 Tormod Volden
+* Copyright 2008 Boisy G. Pitre (parts taken from toolshed/dwdos)
+*
+* Distributed under the GNU General Public License, version 2 or later.
+*
+* For patching BASIC ROM (upper 8KB), replacing DLOAD command:
+* lwasm --pragma=condundefzero -r -b -odwload.bin dwload.asm -DD32ROM
+*
+* Standalone, and using Becker interface
+* lwasm --pragma=condundefzero -r -b -odwload.bin dwload.asm -DBECKER
+*
+* Build a "dweeb" for chainloading by a "normal" build:
+* lwasm -r -b -odwload.bin dwload.asm -DDWEEB
+*
+* Example build for other address:
+* lwasm -r -b -odwload.bin dwload.asm -DDWEEB -DRAMORG=0x600
+********************************************************************
+
+
+* dwload temporary RAM storage
+noexec equ $10 inhibit exec after loading
+bootflag equ $11 zero if run from command line, $55 if autorun on boot
+dnum equ $12 assigned drive number from server
+sstack equ $1cd backup of original stack
+sector equ $1cf counter, used when loading file contents, just below namebuf/DECB header
+reqbuf equ namebuf-1
+namebuf equ $1d1 fixed by BASIC read filename function
+decbhdr equ namebuf DECB headers get copied in here
+startbuf equ namebuf+8 dw input data buffer, can reuse buffer after DECB header slot
+endbuf equ startbuf+256
+tmpstack equ $3fc normally enough unused area below here (goes 30 bytes deep)
+
+* ROM routines used
+OUTCH equ $BCAB print char A to screen
+OUTCHR equ $B54A print char A to DEVNUM
+OUTSTR equ $90E5 print string at X+1 to DEVNUM
+OUTNUM equ $957A print number in D to DEVNUM
+GETFNAM equ $B7AA read file name and length into $1d1
+OKPRMPT equ $8371 BASIC OK prompt, command loop
+IOERROR equ $B84B IO_error
+RUNBASIC equ $849F run_basic, enable IRQs etc
+BASVECT1 equ $841F reset BASIC vectors, reset stack etc
+BASVECT2 equ $83ED initialize BASIC
+SYSERR equ $8344 system error
+BACKSPC equ $9A89 print a backspace to DEVNUM
+
+
+ IFNDEF RAMORG
+ IFDEF DWEEB
+RAMORG equ $0E00
+ ELSE
+RAMORG equ $7400
+ ENDC
+ ENDC
+
+ IFDEF D32ROM
+Top equ $BE7F Dragon 32 unused ROM space
+ ELSE
+Start equ RAMORG
+ ENDC
+
+* Entry point from command line (DLOAD or EXEC)
+ IFDEF D32ROM
+ org $A049 DLOAD dispatch
+ ELSE
+ org Start
+
+ IFDEF DW4
+ ldx #goturbo
+ ldy #1
+ lbsr DWWrite
+ ldx #$A000
+Spint leax -1,x
+ bne Spint
+ bra Entry
+goturbo fcb $E6
+ ENDC
+
+ ENDC
+* for later to see that we came from DLOAD command
+ clr <bootflag clear our autoboot flag
+ ldx #dwtext-1
+ jsr OUTSTR print string
+
+Entry
+ IFDEF DWEEB
+ ldu ,s get stacked PC
+ ldx 1,u
+ stx DWReadv
+ ldx 3,u
+ stx DWWritev
+ ldx 5,u
+ stx DoReadv
+ ENDC
+
+ orcc #IntMasks disable FIRQ, IRQ
+
+* CoCo 1/2 Initialization Code (from toolshed/dwdos)
+ ldx #PIA1Base PIA1
+ IFDEF HWINIT
+ clr -3,x clear PIA0 Control Register A
+ clr -1,x clear PIA0 Control Register B
+ clr -4,x set PIA0 side A to input
+ ldd #$FF34
+ sta -2,x set PIA0 side B to output
+ stb -3,x enable PIA0 peripheral reg, disable PIA0
+ stb -1,x MPU interrupts, set CA2, CA1 to outputs
+ clr 1,x $FF20 = DDR, motoroff
+ clr 3,x $FF22 = DDR, sound disabled
+ deca A = $FE after deca
+ sta ,x bits 1-7 are outputs, bit 0 is input on PIA1 side A
+ lda #$F8
+ sta 2,x bits 0-2 are inputs, bits 3-7 are outputs on B side
+ stb 1,x enable peripheral registers, disable PIA1 MPU
+ stb 3,x interrupts and set CA2, CB2 as outputs
+ ENDC
+ ldb #$02
+ stb ,x make RS-232 output marking
+ IFDEF HWINIT
+ aslb
+ clr -2,x
+ bitb 2,x
+
+ lda #$37
+ sta PIA1Base+3
+
+ lda PIA0Base+3
+ ora #$01
+
+ IFDEF D32ROM
+ bra dload2 continue in next dload hunk
+eoclob1 equ * must be below or equal $A08B (FM error used by cloadm) !
+ org $a0f4
+dload2
+ ENDC
+
+ sta PIA0Base+3
+
+ lda PIA1Base+2
+ anda #$07
+ sta PIA1Base+2
+ ENDC
+
+ IFNDEF DWEEB
+* Spin for a while so that the RS-232 bit stays hi for a time
+Reset
+ ldx #$A000
+Spin leax -1,x
+ bne Spin
+
+* Request named object from DW server
+ lda <bootflag coming from autoboot?
+ lbne autoreq then use default name
+ ENDC
+ jsr <$a5 peek at next character
+* beq noname end of line peeked
+ suba #'N DLOADN ?
+ sta <noexec 0 = noexec
+ bne getn
+ jsr <$9f read next char (the N)
+* or here, after reading the zero character?
+getn jsr GETFNAM read file name and length into $1d1 = namebuf
+ ldx #namebuf-1 packet buffer start
+ clr ,x zero MSB for Y
+ ldy ,x++ length of file name (16 bit)
+ lbeq noname no file name given?
+ ldb -1,x length of name (8 bit)
+ clr b,x zero terminate name string (for error)
+ inc ,--x 1 = DriveWire OP_NAMEOBJ_MOUNT
+ leay 2,y length of DW packet, name length + 2
+
+ IFDEF D32ROM
+ IFNDEF HWINIT
+ bra dload2 continue in next dload hunk
+eoclob1 equ * must be below or equal $A08B (FM error used by cloadm) !
+ org $a0f4
+dload2
+ ENDC
+ ENDC
+
+reqobj
+ jsr DWWrite
+ ldx #dnum Our drive number variable
+ clr ,x
+ leay 1,y read one byte back (Y is 0 after DWWrite)
+ jsr DWRead get drive number
+ tst ,x
+ bne ReadDECB successful mount
+ tst <bootflag
+ lbne stealth silent failure, BASIC OK prompt
+ ldb #$19 MO ERROR
+ jmp SYSERR system error
+autoreq sta <noexec a is non null, autoexec
+noname ldx #autoname
+ ldy #(autonend-autoname) length of DW packet
+ bra reqobj
+
+* named object has been mounted, proceed to read in file
+ReadDECB
+ ldx #0000
+ stx sector
+ ldu #endbuf * start with empty buffer
+ ldx #tmpstack * our temporary stack location
+ exg x,s * move stack here
+ stx sstack * save original stack pointer
+* read DECB header
+nextseg ldy #5
+ ldx #decbhdr * copy DECB header here
+ jsr copybuf * moves x ahead
+ lda -5,x * DECB segment header starts with zero
+ beq ml * normal data segment
+
+ cmpa #$55 * Dragon DOS file?
+ bne noddd
+ leay 4,y * remaining header bytes (y is 0 here)
+ jsr copybuf
+
+ dec -8,x * Dragon DOS BASIC = 1
+ bne ddbin
+ leax -1,x * length at x-5
+ bra ldbas
+
+ddbin ldy -5,x * length
+ ldx -7,x * load address
+ jsr copybuf * read whole file
+
+ ldx #decbhdr+8 * exec address ptr + 2
+ bra oldsp
+* sty #decbhdr+4 * clear out new sp
+* ldx #decbhdr+8 * exec address ptr + 2
+* bra endseg
+
+noddd inca
+ lbne ErrDWL * must be $FF otherwise
+ leay 1,y * Y is 0 after copybuf
+ cmpy sector * only first sector can be BASIC header
+ bne endseg * otherwise end flag
+ cmpu #startbuf+5 * must be first segment also
+ bne endseg
+* loading DECB BASIC file
+* bytes 4 and 5 are actually part of the program
+ leau -2,u * u was 5 bytes into read buffer here
+
+* at this point x is past 5-byte header, u is 3 bytes into first 256-bytes block
+* for Dragon DOS x is 8 bytes into header, u is 9 bytes into first 256-bytes block
+ldbas ldy -4,x * read whole BASIC program
+ ldx <$19
+ jsr copybuf
+ jsr prbang
+* set up BASIC pointers and finish
+ stx <$1b * end of BASIC program
+ stx <$1d
+ stx <$1f
+ tst <noexec
+ lbeq $B72D * print OK, run BASVECT1, BASVECT2, readline
+ jsr BASVECT1 * BasVect1 reset BASIC stack etc
+ jsr BASVECT2 * BasVect2 initialize BASIC
+ jmp RUNBASIC * run_basic
+
+ml ldy -4,x * DECB segment length
+ ldx -2,x * DECB segment loading address
+ jsr copybuf
+ bra nextseg
+
+prbang jsr BACKSPC * print backspace to devnum
+ lda #'! * print bang
+ jmp OUTCHR * print to devnum
+
+endseg
+ ldu -4,x * new stack pointer specified?
+ bne setsp
+oldsp ldu sstack * otherwise restore original SP
+setsp tfr u,s
+ bsr prbang
+ IFNDEF FUZIX
+ andcc #~IntMasks * enable interrupts
+ ENDC
+ ldx -2,x * exec address
+ tfr x,d
+ inca
+ beq retbas * return to basic if exec address $FFxx
+ stx <$9d * save BASIC EXEC address
+ tst <noexec
+ beq retbas
+ IFDEF FUZIX
+ jmp ,x * don't use stack and don't look back
+ ELSE
+ jsr ,x * run loaded program
+ ENDC
+retbas rts
+
+* vector table for chainloaders etc
+ fdb DWRead
+ fdb DWWrite
+ fdb DoRead
+ fdb 0
+
+dwtext fcc /DWLOAD/
+ fcb $0D,0
+
+ IFDEF D32ROM
+eoclob2 equ * must be below or equal $A1CC !
+
+* Hook DWLOAD into boot code
+* Use "non-invasive" location to avoid issues with programs copying
+* parts of the boot code to perform hardware initialisation.
+* Use JSR to record where we are coming from.
+ org $b466 overwrite end of boot code
+ jsr fromboot is originally a jump to command loop
+
+* rest of code goes to top of ROM
+
+ org Top
+
+fromboot
+ ldu ,s++ check return address (and drop it)
+ cmpu #$b469 ROM code location (not a copy)
+ bne gocmdl return if run from a copied code segment
+ cmpx #$B44F coldstart sets this, warmstart doesn't
+ bne gocmdl return if warmstart
+
+* check for SHIFT key
+chkshift lda $FF02 save PIA
+ ldb #$7F
+ stb $FF02
+ ldb $FF00
+ sta $FF02 restore PIA
+ comb
+ andb #$40
+ bne gocmdl return if shift key pressed
+
+ incb B was 0 before
+ stb <bootflag our autoboot flag = 1
+ jsr Entry
+ bra gocmdl
+ ENDC
+
+autoname fcb $01 OP_NAMEOBJ_MOUNT
+ fcb (autonend-autoname-2) length of name string
+ IFDEF FUZIX
+ fcc /fuzix.bin/
+ ELSE
+ fcc /AUTOLOAD.DWL/
+ ENDC
+autonend
+
+ErrDWL lbra IOERROR BASIC IO ERROR
+stealth andcc #~IntMasks enable interrupts
+gocmdl jmp OKPRMPT BASIC OK prompt
+* does SP need to be restored on error?
+
+* copy y chars from read buffer to x, updates u
+copybuf
+copyl cmpu #endbuf
+ bne copym
+* fill up buffer via DW - resets buffer pointer u
+ pshs x,y
+ ldx sector
+ ldy #startbuf
+ tfr y,u
+ bsr DoRead
+ bcs ErrDWL
+ bne ErrDWL
+ leax 1,x
+ stx sector
+ lda #'. print dot
+ jsr OUTCHR
+ puls x,y
+copym lda ,u+
+ IFDEF FUZIX
+ clr $FFBF switch in memory cartridge
+ ENDC
+ sta ,x+
+ IFDEF FUZIX
+ clr $FFBE
+ ENDC
+ leay -1,y
+ bne copyl
+ rts
+
+
+* also used by DWRead/DWWrite
+PIA0Base equ $FF00
+PIA1Base equ $FF20
+IntMasks equ $50
+
+ IFDEF DWEEB
+DoRead fcb $7E
+DoReadv fdb 0
+DWRead fcb $7E
+DWReadv fdb 0
+DWWrite fcb $7E
+DWWritev fdb 0
+ end Entry * or Start
+ ENDC
+
+* below code is taken from toolshed/dwdos
+
+DoRead
+ lda <dnum our drive number
+ clrb LSN bits 23-16
+ pshs d,x,y
+ lda #OP_READEX
+ReRead pshs a
+ leax ,s
+ ldy #$0005
+ lbsr DWWrite
+ puls a
+
+ ldx 4,s get read buffer pointer
+ ldy #256 read 256 bytes
+ ldd #133*1 1 second timeout
+ bsr DWRead
+ bcs ReadEx
+ bne ReadEx
+* Send 2 byte checksum
+ pshs y
+ leax ,s
+ ldy #2
+ lbsr DWWrite
+ ldy #1
+ ldd #133*1
+ bsr DWRead
+ leas 2,s
+ bcs ReadEx
+ bne ReadEx
+* Send 2 byte checksum
+ lda ,s
+ beq ReadEx
+ cmpa #E_CRC
+ bne ReadErr
+ lda #OP_REREADEX
+ clr ,s
+ bra ReRead
+ReadErr comb
+ReadEx puls d,x,y,pc
+
+* Used by DWRead and DWWrite
+CoCo equ 1
+NOINTMASK equ 1
+Level equ 1
+Carry equ 1
+DAT.Regs equ $FFA0
+E$NotRdy equ 246
+Vi.PkSz equ 0
+V.SCF equ 0
+
+ IFEQ DW4-1
+ use dw4read.s
+ use dw4write.s
+ ELSE
+ use dwread.s
+ use dwwrite.s
+ ENDC
+
+ use dw.def
+
+csize equ *-Entry
+eom equ *-Top
+
+* Fill pattern
+
+ end Entry
+ ENDC
+
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