org 100h

start:
          mvi  a,00
          mov  c,a
          sta  curdsk
          call setdrv
          mvi a,2        ; set track 2
          call settrk  
          call redtrk   
          mvi  a,01      ; select drive b
          call setdrv  
          mvi  a,2      
          call settrk  
          call wrttrk
          jmp  0


trkreg    equ  0e3fdh    ; Morrow DJ2B track register

settrk:
          mov  c,a       ; Enter with track # in acc
          sui  30h       ; Force binary, if not already
          cpi  77        ; Test for legal range.
maxtrk    equ  $-1       ; Set in proper max track #+1
          jnc  trkerr
          cpi  00h
          jc   trkerr    ; Negatives not allowed
          sta  curtrk    ; Make it current track
          call notbsy    ; Make sure 1791 is idle
          sta  trkreg    ; and load track register
          adi  30h       ; Make it ascii for possible
          sta  asctrk    ; use elsewhere. 
          ret
trkerr:
          call ccrlf
          call spmsg     
          db   ' Track number not acceptable.',0
          xra  a         ; Set z flag
          ret

curtrk    db   1         ; CMDREG is part of SELCTDRV.LIB
asctrk    db   1


datreg    equ  0fbffh    ; Morrow DJ2B 1791 data port
cmdreg    equ  0fbfch    ; Morrow DJ2B 1791 command port
rtkcmd    equ  000e4h    ; 1791 read track command

redtrk:
          call notbsy    ; Wait until 1791 is idle
          lxi  d,datreg  ; Look at 1791 data register
          lxi  h,trkbuf  ; and set up buffer area
          mvi  c,24      ; Load number of pages
Šmaxpag    equ  $-1       ; to be read from track. 
          mvi  a,rtkcmd  ; Load and issue track read
          sta  cmdreg    ; command for the 1791
datain:
          ldax d         ; Load data byte
          mov  m,a       ; and store in buffer.
          inr  l
          jnz  datain    ; Loop until all written.
          inr  h
          dcr  c
          jnz  datain
          ret


djcont    equ  0e3f9h    ; Morrow DJ2B drive control port
djfunc    equ  0e3fah    ; Morrow DJ2B drive function port 


djdriv    equ  0d31bh    ; Morrow DJ2B BIOS setdrive entry
djfunc    equ  0e3fah    ; Morrow DJ2B drive function port 

setdrv:                                                    
          mov  a,c       ; Save desired disk (in C on entry)
          ori  30h       ; Make ascii if not already
          sta  ascdsk    ; and save it for possible use
          ani  07h       ; Mask off to binary 
          sta  curdsk
          call djdriv    ; Use the BIOS routine      
          ret

curdsk    db   1
ascdsk    db   1

wrtcmd    equ       000f4h    ; Write track command

wrttrk:
          call notbsy         ; Wait until 1791 idle
          lxi  d,datreg       ; Point to 1791 data port
          lxi  h,trkbuf      ; and to source code.
          mvi  c,24           ; Set number of pages to be
wrtpag    equ  $-1            ; written to disk
          mvi  a,wrtcmd       ; Get and issue a write
          sta  cmdreg         ; track command.
          xchg                ; Swap the pointers-

wrtlup:
          ldax d              ; Get a data byte and dump 
          mov  m,a            ; it into the 1791. Then
          inr  e              ; update the byte pointer to
          jnz  wrtlup         ; the next cell and continue
          inò  ä              »  untiì thå entirå buffeò haó �
          dcr  c              ; been written to disk : one
          jnz  wrtlup         ; entire track's worth.
          ret

Š
spmsg:    xthl
readit:   mov  a,m
          ora  a
          jz   done
          inr l
          jnz readit
          inr  h
          jmp  readit
done:     xthl
          ret
trkbuf    ds   17ffh





notbsy:
          mvi  c,10           ; Preset counter

wait1:
          lxi  h,cmdreg       ; Point to command port of
          mov  a,m            ; 1791 and get a status byte.
          rar                 ; Test busy flag - if not up,
          jnc  timeot         ; wait for it to come up for 
                              ; short period.
wait2:
          mov  a,m            ; Get status byte and test for
          rar                 ; busy flag up. Loop until it
          jc   wait2          ; comes down again.
          ret                 ; 1791 idle, go home.

timeot:   dcr  c              ; Don't look for flag to come up
          jnz  wait1          ; forever. If no busy flag by
          ret                 ; ten tries, is not coming up.


ccrlf:   
          mvi  a,0dh
          call co
          mvi  a,0ah
          call co

co:       mvi  c,2
          call 5
          ret