;; KC compact disc interface uses a patched AMSDOS ROM
;;
;; Differences:
;; - Read data (C666) has been patched to support double sided discs.
;; bit 2 = side, bit 1,0 = drive
;; 
;; - |CPM has been patched to recognise Microdos format and to boot Microdos discs.
;;
;; - step rate has been speeded up
;;
;; - CR,LF message has had CR,LF swapped around. No effect.
;;
;; - Two chars ":" and ";" in invalid chars for filename have been swapped. No effect.
;;
;; - Supports 4 "drives", drives 2 and 3 are ram discs.
;;
;; - If drive 2 or 3 are selected, then it stops auto detect. Then when disc motor is turned on/off it actually
;; stores data to ram. Implements a kind of ram disc.
;;

;; The following are the changed data.. All other data is the same
 
;; |CPM function
;; CP/M function "boot"

;;---------------------------------------------------------------------
;; Original AMSDOS rom
c1b2 cd12b9    call    $b912			; firmware function: HI: KL CURR SELECTION
c1b5 4f        ld      c,a
c1b6 21dcc1    ld      hl,$c1dc
c1b9 c316bd    jp      $bd16			; firmware function: MC START PROGRAM

;;---------------------------------------------------------------------
;; KC Compact disc ROM
;; C1B7, B8 are different

c1b2 cd12b9    call    &b912			; firmware function: HI: KL CURR SELECTION
c1b5 4f        ld      c,a
c1b6 2184dd    ld      hl,&dd84				
c1b9 c316bd    jp      &bd16			; firmware function: MC START PROGRAM


;;---------------------------------------------------------------------
;; Original AMSDOS rom 

c4ef ff        rst     $38			;; unused

;; setup XDPB
c4f0 79        ld      a,c
c4f1 fe02      cp      $02

;;---------------------------------------------------------------------
;; KC Compact disc ROM
c4ef 38								;; unused

;; setup XDPB
c4f0 c30cdc    jp     $dc0c


;;---------------------------------------------------------------------
;; Original AMSDOS ROM

;; Displaying a directory entry

;; display file size
d598 210c00    ld      hl,$000c


;;---------------------------------------------------------------------
;; KC Compact disc ROM
c598 c306dc    jp      &dc06


;;-------------------------------------------------------------------------
;; Original AMSDOS ROM

;; default BIOS: SETUP DISC parameters
c5d4:
defw &0032			;; motor on time in 20ms units
defw &00fa			;; motor off time in 20ms units
defb &af			;; write off time in 10ms units
defb &0f			;; head settle time in 1ms units
defb &0c			;; step rate in 1ms units
defb &01			;; head unload delay
defb &03			;; head load delay and dma flag


;;-------------------------------------------------------------------------
;; KC Compact ROM
;;
;; Step rate is quicker than for CPC

;; default BIOS: SETUP DISC parameters
c5d4:
defw &0032			;; motor on time in 20ms units
defw &00fa			;; motor off time in 20ms units
defb &af			;; write off time in 10ms units
defb &0f			;; head settle time in 1ms units
defb &04			;; step rate in 1ms units
defb &01			;; head unload delay
defb &03			;; head load delay and dma flag


;;----------------------------------------------------
;; Original AMSDOS ROM 
c666 cd76c9    call    $c976			;; spin up motor
c669 3e66      ld      a,$66			;; read data (mfm, skip)
c66b 0610      ld      b,$10
c66d 2262be    ld      ($be62),hl

;;----------------------------------------------------
;; KC Compact ROM
;; E = drive/side
;; bit 2 = side
;; bit 1,0 = drive

c666 3e66      ld      a,&66			
c668 cd76c9    call    &c976			;; spin up motor
c66b 0610      ld      b,&10
c66d c303dc    jp      &dc03			;; read data patched to read double sided discs

;;----------------------------------------------------
;; Original AMSDOS ROM 

;; enabling motor or not...
c976 2276be    ld      ($be76),hl

;;----------------------------------------------------
;; KC Compact ROM

;; if you don't enable motor or not
c976 c309dc    jp      &dc09

;;-------------------------------------------------
;; Original AMSDOS ROM
;; In get address of XDPB 
ca64 2a42be    ld      hl,($be42)		; HL = XDPB for drive 0 


;;-------------------------------------------------
;; KC Compact ROM
ca64 c300dc    jp      &dc00

;;-------------------------------------------------
;; Original AMSDOS ROM
cb86 0d        dec     c
cb87 0a        ld      a,(bc)
cb88 ff        rst     &38

;;-------------------------------------------------
;; KC Compact ROM
;;
;; CR,LF have been reversed

cb86 0a        ld      a,(bc)
cb87 0d        dec     c
cb88 ff        rst     &38

;;-------------------------------------------------
;; Original AMSDOS ROM

;; table of invalid characters for filename
dbb2 
defb '<'
defb '>'
defb '.'
defb ','
defb ';'
defb ':'
defb '='
defb '['
defb ']'
defb '_'
defb '%'
defb '|'
defb '('
defb ')'
defb '/'
defb '\'
defb &7f
defb 0

;;-------------------------------------------------
;; KC Compact ROM
;; : and ; are swapped in table

;; table of invalid characters
dbb2 
defb '<'
defb '>'
defb '.'
defb ','
defb ':'
defb ';'
defb '='
defb '['
defb ']'
defb '_'
defb '%'
defb '|'
defb '('
defb ')'
defb '/'
defb '\'
defb &7f
defb 0

;;-------------------------------------------------
;; Original AMSDOS ROM
;; &dc00-&dfff all filled with &ff

;;-------------------------------------------------
;; KC Compact disc ROM

;; called in get address of XDPB
dc00 c30fdc    jp      &dc0f

;; read data patched to allow reading of double sided discs
dc03 c321dc    jp      &dc21

;; called when displaying a directory
dc06 c399dc    jp      &dc99

dc09 c3abdc    jp      &dcab

dc0c c3f2dc    jp      &dcf2

;;---------------------------------------------------------
;; expanded disc param block for drive B?
dc0f 6f        ld      l,a
dc10 7b        ld      a,e
dc11 d601      sub     &01
dc13 7d        ld      a,l
dc14 2a42be    ld      hl,(&be42)
dc17 114000    ld      de,&0040
dc1a 3801      jr      c,&dc1d
dc1c 19        add     hl,de
dc1d 5f        ld      e,a
dc1e 19        add     hl,de
dc1f d1        pop     de
dc20 c9        ret     

;;---------------------------------------------------------
;; called in read data
;; H = command byte

dc21 2262be    ld      (&be62),hl
dc24 67        ld      h,a
dc25 69        ld      l,c
dc26 2274be    ld      (&be74),hl
dc29 48        ld      c,b
dc2a 2130dc    ld      hl,&dc30
dc2d c3ffc6    jp      &c6ff					;; execute function with retry

;; function to call
dc30 2a74be    ld      hl,(&be74)
dc33 017efb    ld      bc,&fb7e
dc36 7c        ld      a,h				;; command byte
dc37 cd5cc9    call    &c95c 			;; fdc send command byte
dc3a 7d        ld      a,l
dc3b e63f      and     &3f
dc3d 6f        ld      l,a
dc3e 3e10      ld      a,&10			;; XDPB: sectors/track
dc40 cd5cca    call    &ca5c			;; get XDPB parameter by index
dc43 bd        cp      l
dc44 2e00      ld      l,&00
dc46 3003      jr      nc,&dc4b
dc48 cbd3      set     2,e				;; side 2 
dc4a 6f        ld      l,a
dc4b 3a74be    ld      a,(&be74)
dc4e 95        sub     l
dc4f 6f        ld      l,a

dc50 7b        ld      a,e				;; drive/side
dc51 cd5cc9    call    &c95c 			;; fdc send command byte

dc54 7c        ld      a,h
dc55 fe4d      cp      &4d				;; format
dc57 2019      jr      nz,&dc72

dc59 cb93      res     2,e				;; side 0

dc5b 3e14      ld      a,&14			;; N sector size
dc5d cd59c9    call    &c959			;; write XDPB parameter to FDC
dc60 3e10      ld      a,&10			;; sectors/track
dc62 cd59c9    call    &c959			;; write XDPB parameter to FDC
dc65 3e12      ld      a,&12			;; gap length for format
dc67 cd59c9    call    &c959			;; write XDPB parameter to FDC
dc6a 3e13      ld      a,&13		;; filler byte
dc6c cd5cca    call    &ca5c		;; get XPDB parameter by index
dc6f c3c1c6    jp      &c6c1		;; send last byte and then transfer execution phase

dc72 7a        ld      a,d			;; C
dc73 cd5cc9    call    &c95c ;; fdc send command byte
									;; H
dc76 7b        ld      a,e
dc77 e604      and     &04			;; take bit 2 of drive/side specified and transfer into bit 0
dc79 cb3f      srl     a
dc7b cb3f      srl     a			
dc7d cd5cc9    call    &c95c ;; fdc send command byte
dc80 cb93      res     2,e
dc82 7d        ld      a,l			;; R
dc83 cd5cc9    call    &c95c ;; fdc send command byte
dc86 3e14      ld      a,&14		;; sector size
dc88 cd59c9    call    &c959	;; write XDPB parameter to FDC
dc8b 7d        ld      a,l			;; EOT
dc8c cd5cc9    call    &c95c ;; fdc send command byte
dc8f 3e11      ld      a,&11		;; gap length read/write
dc91 cd59c9    call    &c959	;; write XDPB parameter to FDC
dc94 3eff      ld      a,&ff		;; data length
dc96 c3c1c6    jp      &c6c1	 ;; send last byte and then transfer execution phase

;;---------------------------------------------------------
dc99 1152dd    ld      de,&dd52			;; data format
dc9c fec0      cp      &c0
dc9e 2803      jr      z,&dca3

dca0 116bdd    ld      de,&dd6b			;; other format

dca3 011900    ld      bc,&0019
dca6 eb        ex      de,hl
dca7 edb0      ldir    
dca9 37        scf     
dcaa c9        ret     

;;---------------------------------------------------------
dcab 2276be    ld      (&be76),hl
dcae f5        push    af
dcaf 3e18      ld      a,&18				;; auto select
dcb1 cd5cca    call    &ca5c				;; get XDPB parameter by index
dcb4 fe01      cp      &01
dcb6 cabddc    jp      z,&dcbd				;; signal to not detect format?

dcb9 f1        pop     af
dcba c379c9    jp      &c979				;; standard motor control

;; do not detect format is signalled
;; HL = address of buffer for read/write
;; A = command byte to execute
dcbd f1        pop     af
dcbe e5        push    hl
dcbf d5        push    de
dcc0 c5        push    bc
dcc1 47        ld      b,a
dcc2 3e13      ld      a,&13				;; filler byte
dcc4 cd5cca    call    &ca5c				;; get XDPB parameter by index
dcc7 82        add     a,d					;; ?
dcc8 cb21      sla     c
dcca 51        ld      d,c
dccb 1e00      ld      e,&00
dccd 21003e    ld      hl,&3e00
dcd0 19        add     hl,de
dcd1 f3        di      
											;; A = organization to use
dcd2 cd5bbd    call    &bd5b				;; KL BANK SWITCH
dcd5 f5        push    af					;; store previous organization
dcd6 ed5b76be  ld      de,(&be76)			;; buffer for sector read/write
dcda 78        ld      a,b
dcdb fe66      cp      &66					;; read data?
dcdd 2801      jr      z,&dce0

dcdf eb        ex      de,hl
dce0 010002    ld      bc,&0200
dce3 edb0      ldir    
dce5 f1        pop     af						;; A = organization to use
dce6 cd5bbd    call    &bd5b				;; KL BANK SWITCH
dce9 fb        ei      
dcea c1        pop     bc
dceb d1        pop     de
dcec e1        pop     hl
dced f1        pop     af
dcee 3e00      ld      a,&00
dcf0 37        scf     
dcf1 c9        ret     

;;---------------------------------------------------------

;; C = drive
;;
;; if drive is 2 or 3
;; then it selects a special format and doesn't allow auto detect
dcf2 79        ld      a,c
dcf3 fe04      cp      &04
dcf5 210000    ld      hl,&0000
dcf8 d0        ret     nc				;; quit if drive > 4

dcf9 d5        push    de
dcfa 116bdd    ld      de,&dd6b			;; 9 sectors per track, sector id &1, auto detect
dcfd fe01      cp      &01
dcff 280a      jr      z,&dd0b

dd01 1120dd    ld      de,&dd20		;; do not auto detect (drive 2)
dd04 fe02      cp      &02
dd06 2803      jr      z,&dd0b

dd08 1139dd    ld      de,&dd39			;; do not auto detect (drive 3)

;; copy it in
dd0b f5        push    af
dd0c c5        push    bc
dd0d 2a42be    ld      hl,(&be42)
dd10 014000    ld      bc,&0040
dd13 09        add     hl,bc
dd14 eb        ex      de,hl
dd15 011900    ld      bc,&0019
dd18 edb0      ldir    
dd1a c1        pop     bc
dd1b f1        pop     af
dd1c d1        pop     de
dd1d c3f7c4    jp      &c4f7				;; continue with AMSDOS detect code


;; filler byte defines where to put data?

;; 32 sectors per track
;; sector id &01
dd20:
defb &80,&00,&03,&07,&00,&3f,&00,&1f,&00,&80,&00,&00,&00,&00,&00,&01,&20,&2a,&52,&c4,&02,&04,&00,&00,&01

;; 32 sectors per track
;; sector id &01
dd39:
defb &80,&00,&05,&0f,&03,&5f,&00,&7f,&00,&80,&00,&00,&00,&00,&00,&01,&20,&2a,&52,&e8,&02,&04,&00,&00,&01

;; 9 sectors per track
;; sector id &c1
dd52:
defb &20,&00,&03,&07,&00,&b3,&00,&3f,&00,&c0,&00,&10,&00,&00,&00,&c1,&09,&2a,&52,&e5,&02,&04,&00,&00,&00

;; 9 sectors per track
;; sector id &01
dd6b:
defb &48,&00,&05,&1f,&03,&b0,&00,&7f,&00,&80,&00,&10,&00,&01,&00,&01,&09,&2a,&52,&e5,&02,&04,&00,&00,&00

;;-------------------------------------------------------------------------
;; |CPM patch to recognise and boot Microdos

dd84 cd76c9    call    &c976				;; spin up motor
dd87 1600      ld      d,&00
dd89 0e10      ld      c,&10
dd8b 215dc5    ld      hl,&c55d				;; read id
dd8e cdffc6    call    &c6ff				;; execute function with retry
dd91 d2dcc1    jp      nc,&c1dc				;; jump to normal (CPC) cpm boot

;; This checks the ID. It will bail out if it finds a CPC sector ID
;; e.g. &c1 or &41
dd94 3a51be    ld      a,(&be51)			;; R from result phase/ID field
dd97 e6c0      and     &c0
dd99 c2dcc1    jp      nz,&c1dc				;; jump to normal (CPC) cpm boot

;; bit 7,6 must both be zero to get here

dd9c 3a52be    ld      a,(&be52)			;; N from result phase/ID field
dd9f fe03      cp      &03
dda1 c2dcc1    jp      nz,&c1dc				;; jump to normal (CPC) cpm boot

;; Sector size must be 3 (1024 byte sectors)

dda4 f3        di      

dda5 21fdde    ld      hl,&defd
dda8 11053f    ld      de,&3f05				;; n, eot, gpl, dtl
ddab 010400    ld      bc,&0004
ddae edb0      ldir    

;; boot from drive 0
ddb0 3e00      ld      a,&00
ddb2 32013f    ld      (&3f01),a

ddb5 0605      ld      b,&05
ddb7 c5        push    bc

ddb8 af        xor     a					;; track 0
ddb9 32023f    ld      (&3f02),a			;; c
ddbc 32033f    ld      (&3f03),a			;; h
ddbf 3e01      ld      a,&01
ddc1 32043f    ld      (&3f04),a			;; r
ddc4 3e05      ld      a,&05
ddc6 32063f    ld      (&3f06),a			;; eot

;; read data
;; 3f00 = command
;; 3f01 = drive/side
;; 3f02 = c
;; 3f03 = h
;; 3f04 = r
;; 3f05 = n
;; 3f06 = eot
;; 3f07 = gpl
;; 3f08 = dtl

;; seek:
;; 3f00 = command
;; 3f01 = drive
;; 3f02 = track


ddc9 cd5fde    call    &de5f				;; seek
ddcc c253de    jp      nz,&de53

											;; track 0, sector 1, side 0
ddcf 21803f    ld      hl,&3f80				;; 3f80
ddd2 f3        di      
ddd3 cdccde    call    &decc				;; read sector
ddd6 c253de    jp      nz,&de53

ddd9 3e01      ld      a,&01				
dddb 32033f    ld      (&3f03),a			;; h
ddde 32043f    ld      (&3f04),a			;; r

dde1 3e04      ld      a,&04				;; drive 0, side 1
dde3 32013f    ld      (&3f01),a

											;; track 0, sector 1, side 1
dde6 cd5fde    call    &de5f				;; seek
dde9 2068      jr      nz,&de53

ddeb 218053    ld      hl,&5380				;; 5380
ddee cdccde    call    &decc				;; read sector
ddf1 2060      jr      nz,&de53
ddf3 3e00      ld      a,&00				;; drive 0, side 0
ddf5 32013f    ld      (&3f01),a
ddf8 af        xor     a
ddf9 32033f    ld      (&3f03),a			;; h
ddfc 3c        inc     a					;; =1 
ddfd 32043f    ld      (&3f04),a			;; r
de00 32023f    ld      (&3f02),a			;; track

de03 cd5fde    call    &de5f			;; seek
de06 204b      jr      nz,&de53
				
										;; track 1, sector 1, side 0
de08 218067    ld      hl,&6780			;; 6780
de0b cdccde    call    &decc			;; read sector
de0e 2043      jr      nz,&de53
de10 3e01      ld      a,&01
de12 32033f    ld      (&3f03),a			;; h
de15 32043f    ld      (&3f04),a			;; r
de18 32023f    ld      (&3f02),a			;; track
de1b 3e04      ld      a,&04
de1d 32013f    ld      (&3f01),a			;; drive 0, side 1
de20 3e01      ld      a,&01
de22 32063f    ld      (&3f06),a			;; eot
de25 cd5fde    call    &de5f			;; seek
de28 2029      jr      nz,&de53

										;; track 1, sector 1, side 1
de2a 21807b    ld      hl,&7b80			;; 7b80
de2d cdccde    call    &decc			;; read sector
de30 2021      jr      nz,&de53

;; ident string:

;; 3f80 = &00
;; 3f81 = &44
;; 3f82 = &4f
;; 3f83 = &53

;; &0,"DOS"

;; perform check on first two chars of ident string
de32 a7        and     a
de33 2a803f    ld      hl,(&3f80)
de36 110044    ld      de,&4400
de39 ed52      sbc     hl,de
de3b c258de    jp      nz,&de58

;; perform check on last two chars of ident string
de3e 2a823f    ld      hl,(&3f82)
de41 114f53    ld      de,&534f
de44 ed52      sbc     hl,de
de46 c258de    jp      nz,&de58

;; execute
de49 3a013f    ld      a,(&3f01)		;; drive/track
de4c fb        ei      
de4d cde5c9    call    &c9e5			;; turn off motor
de50 c30040    jp      &4000			;; execute

;; retry
de53 c1        pop     bc
de54 05        dec     b
de55 c2b7dd    jp      nz,&ddb7
;; we have done enough retries
de58 fb        ei      
de59 cde5c9    call    &c9e5			;; turn off motor
de5c c30000    jp      &0000			;; reset back to BASIC

;;--------------------------------------------------------------------------
;; perform seek
de5f 010f03    ld      bc,&030f			;; 3 bytes, seek command
de62 cd86de    call    &de86			;; write FDC command

;; delay for seek to complete
de65 3e21      ld      a,&21
de67 cdeede    call    &deee
de6a 3d        dec     a
de6b 20fa      jr      nz,&de67

de6d 010801    ld      bc,&0108			;; 1 byte, sense interrupt status
de70 cd8ade    call    &de8a			;; This is a bug. should be &de86
										;; so in effect we will try to execute
										;; command at &3f03

;; normally a sense interrupt status command will return
;; either just &80 
;; or ST0 and current track number
;;
;; The delay above would have waited until the seek had completed.
;; Then the FDC should signal it has completed and we should read it.
										
de73 cd9ede    call    &de9e			;; read FDC data
de76 47        ld      b,a
de77 87        add     a,a
de78 c8        ret     z

de79 cd9ede    call    &de9e			;; read FDC data
de7c 78        ld      a,b
de7d e6f0      and     &f0
de7f fec0      cp      &c0
de81 28ea      jr      z,&de6d

;; here we are checking for seek complete I assume
de83 ee20      xor     &20
de85 c9        ret     

;;--------------------------------------------------------------

;; initial command address
;; C = first byte of command
;; B = number of command bytes
de86 21003f    ld      hl,&3f00
de89 71        ld      (hl),c

;; B = number of command bytes
;; HL = address of command bytes

de8a c5        push    bc
de8b 017efb    ld      bc,&fb7e
de8e ed78      in      a,(c)
de90 e6c0      and     &c0
de92 fe80      cp      &80
de94 20f8      jr      nz,&de8e
de96 0c        inc     c
de97 04        inc     b
de98 eda3      outi    
de9a c1        pop     bc
de9b 10ed      djnz    &de8a
de9d c9        ret     

;;--------------------------------------------------------------
;; read FDC data
de9e c5        push    bc
de9f 017efb    ld      bc,&fb7e
dea2 ed78      in      a,(c)
dea4 e6c0      and     &c0
dea6 fec0      cp      &c0
dea8 20f8      jr      nz,&dea2
deaa 0c        inc     c
deab ed78      in      a,(c)
dead c1        pop     bc
deae c9        ret     

;;--------------------------------------------------------------
;; read FDC result phase
deaf 0607      ld      b,&07
deb1 21093f    ld      hl,&3f09
deb4 cd9ede    call    &de9e			;; read FDC data
deb7 77        ld      (hl),a
deb8 23        inc     hl
deb9 10f9      djnz    &deb4
debb 21093f    ld      hl,&3f09
debe 7e        ld      a,(hl)
debf e6c0      and     &c0
dec1 d640      sub     &40
dec3 2004      jr      nz,&dec9
dec5 23        inc     hl
dec6 cb7e      bit     7,(hl)
dec8 c0        ret     nz

dec9 af        xor     a
deca 3d        dec     a
decb c9        ret     

;;--------------------------------------------------------------
;; read sector
;; HL = address to load sector to
decc e5        push    hl
decd 014609    ld      bc,&0946		;; 9 bytes, first command byte &46 = read data
ded0 cd86de    call    &de86		;; write FDC command
ded3 e1        pop     hl
ded4 cddcde    call    &dedc		;; read FDC execution phase
ded7 cdafde    call    &deaf		;; read FDC result phase
deda a7        and     a
dedb c9        ret     

;;--------------------------------------------------------------
;; read execution phase from FDC
dedc 017efb    ld      bc,&fb7e
dedf ed78      in      a,(c)
dee1 f2dfde    jp      p,&dedf
dee4 e620      and     &20
dee6 c8        ret     z

dee7 0c        inc     c
dee8 eda2      ini     
deea 04        inc     b
deeb 0d        dec     c
deec 18f1      jr      &dedf


;;--------------------------------------------------------------
;; perform a delay
deee f5        push    af
deef 3e0a      ld      a,&0a
def1 f5        push    af
def2 3efa      ld      a,&fa
def4 3d        dec     a
def5 20fd      jr      nz,&def4
def7 f1        pop     af
def8 3d        dec     a
def9 20f6      jr      nz,&def1
defb f1        pop     af
defc c9        ret     

;;--------------------------------------------------------------
;; copied into ram
defd 03        ;; n 
defe 05        ;; eot
deff 1e			;; gpl 
df00 ff			;; dtl 

;; In AMSDOS ROM this is code for CPM2.2
;; In KC Compact ROM this is all filled with &ff