A2osX/ProDOS.FX/ProDOS.S.XRW.txt
2020-09-07 22:40:50 +02:00

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AUTO 3,1
*--------------------------------------
XRWDBG .EQ 0
*--------------------------------------
XRW.START cld $D8 to flag language card bank 1 (main)
lda unitnum get unit number.
pha
lsr
lsr
lsr
lsr
sta XRW.UnitIndex
tax
lda XRW.D2SeekTime-1,x
bne .10
lda #30
sta XRW.D2SeekTime-1,x
.10 pla
and #$7F mask off high bit.
sta A2L 0SSS0000 for IO indexing
* make sure other drives in other slots are stopped
eor XRW.LastUnitUsed same slot as last ?
asl
beq L59BD
lda #$01
sta XRW.montimeh
.1 lda XRW.LastUnitUsed
and #$70
tax
beq L59BD branch if no previous ever (boot only).
jsr XRW.CheckMotorOnX check if previous drive running.
beq L59BD branch if stopped.
lda #1
jsr XRW.Wait100usecA
lda XRW.montimeh
bne .1
*--------------------------------------
L59BD lda bloknml
ldx bloknml+1
stx XRW.ReqTrack calculate block's track and sector.
ldy #$05
.1 asl
rol XRW.ReqTrack
dey
bne .1
asl
bcc .2
ora #$10 adjust for upper 4 bits of track
.2 lsr
lsr
lsr
lsr
sta XRW.ReqSector
*--------------------------------------
jsr XRW.Reset
jsr XRW.CheckMotorOn
php save motor on state : NZ if on
lda #$E8 24 up to 0
sta XRW.montimeh
lda unitnum determine drive 1 or 2.
cmp XRW.LastUnitUsed same slot/drive used before ?
sta XRW.LastUnitUsed save it for next time.
php keep results of compare.
asl get drive # into carry.
bcc .3 branch if drive 1 selected.
inx select drive 2.
.3 lda IO.D2.DrvSel1,x
ldx A2L
lda IO.D2.DrvOn,x turn on the drive.
plp was it the same drive ?
beq .5 yes.
plp NZ: indicate drive off by setting z-flag.
ldy #6
.4 jsr XRW.Wait25600usec 150 ms delay before stepping.
dey
bne .4
php Z set
.5 plp was motor on ?
bne L538E if so, don't wait.
* motor was off, wait for it to speed up
.6 lda #1
jsr XRW.Wait100usecA wait 100us for each count in montime
lda XRW.montimeh
bmi .6 count up to 0000
* motor should be up to speed,
* if it looks stopped then the drive is not present
jsr XRW.CheckMotorOn is drive present ?
beq XRW.E.ND
*--------------------------------------
L538E lda A4L get command #
bne .1
jsr XRW.TestWP 0 = status
bcs XRW.E.WP
bra XRW.E.OK
.1 cmp #4 3 = format
bcs XRW.E.IO
cmp #2 Write ?
bne .2
jsr XRW.TestWP
bcs XRW.E.WP
*--------------------------------------
.2 jsr regrwts
bcs XRW.E.IO
inc buf+1
inc XRW.ReqSector
inc XRW.ReqSector
jsr regrwts get 2nd half of block
dec buf+1
bcc XRW.E.OK
XRW.E.IO lda #MLI.E.IO
.HS 2C BIT ABS
XRW.E.WP lda #MLI.E.WRTPROT
.HS 2C BIT ABS
XRW.E.ND lda #MLI.E.NODEV
sec
.HS 2C BIT ABS
XRW.E.OK lda #0
bit IO.D2.DrvOff,x turn off
rts
*--------------------------------------
regrwts ldy #1
sty XRW.RecalibrateCnt
lda A4L get command #
lsr set carry = 1 for read, 0 for write.
bcs .1 must prenibblize for write
jsr XRW.PreNibble
.1 ldy #64
sty XRW.RetryCnt
lda #$fe
sta XRW.BadSeek
.2 jsr XRW.ReadAddr read next address field.
bcc .4 if CC, A = current track
.3 dec XRW.RetryCnt one less chance.
bne .2 branch to retry.
dec XRW.RecalibrateCnt
sec
bmi .9
.DO XRWDBG=1
jsr XRW.DEBUG
.FIN
ldy XRW.UnitIndex
lda #41
sta XRW.D2Trk-1,y
lda #0
sta XRW.D2VolNum-1,y
jsr XRW.Seek
bra .2
.4 cmp XRW.ReqTrack
beq .5
inc XRW.BadSeek
bmi .41
ldx XRW.UnitIndex
lda XRW.D2SeekTime-1,x
bmi .41
asl XRW.D2SeekTime-1,x
.41 lda XRW.ReqTrack
jsr XRW.Seek
bra .2
.5 lda XRW.AddrField.S is this the right sector ?
cmp XRW.ReqSector
bne .3 no, try another sector.
lda A4L read or write ?
lsr the carry will tell.
bcc L53F4 branch if write
jsr XRW.Read
bcs .3 if bad read
.9 rts
L53F4 jmp XRW.Write
*--------------------------------------
* determine if motor is stopped
*
* if stopped, controller's shift register will not be changing.
* return y = 0 and zero flag set if it is stopped.
*--------------------------------------
XRW.CheckMotorOn
ldx A2L
XRW.CheckMotorOnX
ldy #0 init loop counter.
.1 lda IO.D2.RData,x read the shift register.
jsr .9 delay
pha
pla more delay.
cmp IO.D2.RData,x has shift reg changed ?
bne .9 yes, motor is moving.
lda #MLI.E.NODEV anticipate error.
dey no, dec retry counter
bne .1 and try 256 times.
.9 rts
*--------------------------------------
XRW.TestWP ldx A2L
lda IO.D2.ReadProt,x test for write protected
lda IO.D2.ReadMode,x
rol write protect-->carry-->bit 0=1
lda IO.D2.RData,x keep in read mode
rts
*--------------------------------------
* preniblize subroutine (16 sector format)
*
* converts 256 bytes of user data in (buf) into 6 bit nibls in nbuf2.
* high 6 bits are translated directly by the write routines.
*
* on entry: buf is 2-byte pointer to 256 bytes of user data.
*
* on exit: a,x,y undefined. write routine modified to do direct conversion
* of high 6 bits of user's buffer data.
*--------------------------------------
XRW.PreNibble lda buf self-modify the addresses because of
ldy buf+1 the fast timing required.
clc all offsets are minus $AA.
adc #$02 the highest set is buf+$AC.
bcc L58FA branch if no carry,
iny otherwise add carry to high address.
L58FA sta prn3+1 self mod 3
sty prn3+2
sec
sbc #$56 middle set is buf+$56.
bcs L5906 branch if no borrow,
dey otherwise deduct from high.
L5906 sta prn2+1 self mod 2
sty prn2+2
sec
sbc #$56 low set is exactly buf
bcs L5912
dey
L5912 sta prn1+1 self mod 1
sty prn1+2
ldy #$AA count up to 0.
prn1 lda $1000,y warning: self modified. get byte from lowest group.
and #$03 strip high 6 bits.
tax index to 2 bit equivalent.
lda XRW.0000XX00,x
pha save pattern
prn2 lda $1056,y warning: self modified. get byte from middle group.
and #$03
tax
pla restore pattern.
ora XRW.00XX0000,x combine 2nd group with 1st.
pha save new pattern.
prn3 lda $10AC,y warning: self modified. get byte from highest group.
and #$03
tax
pla restore new pattern
ora XRW.XX000000,x and form final nibl.
pha
tya
eor #$FF
tax
pla
sta nbuf2,x save in nibl buffer.
iny inc to next set.
bne prn1 loop until all $56 nibls formed.
ldy buf now prepare data bytes for write16 subr.
dey prepare end address.
sty A2H
lda buf
sta wrefd1+1 warning: the following storage addresses
beq L595F starting with 'wref' are refs into code
eor #$FF space, changed by this routine.
tay index to last byte of page in (buf).
lda (buf),y pre-niblize the last byte of the page
iny with the first byte of the next page.
eor (buf),y
and #$FC
tax
lda XRW.FC2Nib,x get disk 7-bit nible equivalent.
L595F sta pch
beq L596F branch if data to be written is page aligned.
lda A2H check if last byte is even
lsr or odd address. shift even/odd -> carry.
lda (buf),y if even, then leave intact.
bcc L596D branch if odd.
iny if even, then pre-xor with byte 1.
eor (buf),y
L596D sta A1L save result for write routine.
L596F ldy #$FF index to last byte of data to write.
lda (buf),y to be used as a checksum.
and #$FC strip extra bits
sta A1H and save it.
ldy buf+1 now modify address references to
sty wrefa1+2 user data.
sty wrefa2+2
iny
sty wrefa3+2
sty wrefa4+2
sty wrefa5+2
sty wrefa6+2
ldx A2L and lastly, index references to
stx wrefd2+1 controller.
stx wrefd3+1
stx wrefd4+1
stx wrefd5+1
rts
*--------------------------------------
* write subroutine (16 sector format)
*
* writes data from nbuf1 and buf. first nbuf2, high to low then direct
* from (buf), low to high. assumes 1 usec cycle time. self modified code !!
*
* on entry: x = slotnum times 16
*
* on exit: carry set if error (write protect violation).
* if no error, acc=uncertain, x=unchanged, y=0, carry clear.
*--------------------------------------
XRW.Write lda IO.D2.ReadProt,x
lda IO.D2.ReadMode,x
lda nbuf2
sta pcl
lda #$FF sync data.
sta IO.D2.WriteMode,x (5) goto write mode
ora IO.D2.WShift,x (4)
ldy #$04 (2) for five nibls
nop (2)
pha (3)
pla (4)
wsync pha (3) exact timing.
pla (4) exact timing.
jsr wnibl7 (13,9,6) write sync.
dey (2)
bne wsync (3-) must not cross page !
lda #$D5 (2) 1st data mark
jsr wnibl9 (15,9,6)
lda #$AA (2) 2nd data mark
jsr wnibl9 (15,9,6)
lda #$AD (2) 3rd data mark
jsr wnibl9 (15,9,6)
tya (2) zero checksum
ldy #$56 (2) nbuf2 index
bne L583D (3) branch always
* total time in this write byte loop must = 32us !!!
L583A lda nbuf2,y (4) prior 6-bit nibl
*L583D eor nbuf2-1,y (5) xor with current (4+1 : PAGE CROSS)
L583D eor nbuf2-1,y (4) xor with current (NO MORE PAGE CROSS)
tax (2) index to 7-bit nibl
lda XRW.FC2Nib,x (4) must not cross page boundary
* ldx A2L (3) restore slot index
ldx >A2L (4) absolute reference to zero page
sta IO.D2.WLoad,x (5) store encoded byte
lda IO.D2.WShift,x (4) handshake
dey (2)
bne L583A (3-) must not cross page boundary
* end of write byte loop
lda pcl (3) get prior nibl (from nbuf2)
wrefd1 ldy #$00 (2) warning: load value modified by prenib.
wrefa1 eor $1000,y (4) warning: address modified by prenib.
and #$FC (2) strip low 2 bits
tax (2) index to nibl table
lda XRW.FC2Nib,x (4)
wrefd2 ldx #$60 (2) warning: value modified by prenib.
sta IO.D2.WLoad,x (5) write nibl
lda IO.D2.WShift,x (4) handshake
wrefa2 lda $1000,y (4) prior nibl. warning: address modified by prenib.
iny (2) all done with this page ?
bne wrefa1 (3-) loop until page end.
lda pch (3) get next (precalculated & translated) nibl.
beq L58C0 (2+) branch if code written was page aligned.
lda A2H (3) get byte address of last byte to be written.
beq L58B3 (2+) branch if only 1 byte left to write.
lsr (2) test for odd or even last byte (carry set/clear)
lda pch (3) restore nibl to acc.
sta IO.D2.WLoad,x (5)
lda IO.D2.WShift,x (4)
lda A1L (3) = byte 0 of 2nd page xor'd with byte 1 if
nop (2) above test set carry.
iny (2) y=1
bcs L5899 (2+) branch if last byte to be odd.
wrefa3 eor $1100,y (4) warning: address modified by prenib.
and #$FC (2) strip low 2 bits.
tax (2) index to nibl table
lda XRW.FC2Nib,x (4) get nibl
wrefd3 ldx #$60 (2) restore slot index. warning: modified by prenib
sta IO.D2.WLoad,x (5)
lda IO.D2.WShift,x (4)
wrefa4 lda $1100,y (4) warning: modified by prenib
iny (2) got prior nibl, point to next
wrefa5 eor $1100,y (4) warning: modified by prenib
L5899 cpy A2H (3) set carry if this is the last nibl
and #$FC (2) strip low 2 bits
tax (2)
lda XRW.FC2Nib,x (4)
wrefd4 ldx #$60 (2) restore slot. warning: modified by prenib
sta IO.D2.WLoad,x (5)
lda IO.D2.WShift,x (4)
wrefa6 lda $1100,y (4) get prior nibl. warning: modified by prenib
iny (2)
bcc wrefa3 (3-) branch if not the last.
bcs L58B1 (3) waste 3 cycles, branch always.
L58B1 bcs L58C0 (3) branch always.
L58B3 lda >pch (4) absolute reference to zero page
sta IO.D2.WLoad,x (5)
lda IO.D2.WShift,x (4)
pha (3) waste 14 micro-seconds total
pla (4)
pha (3)
pla (4)
L58C0 ldx A1H (3) use last nibl (anded with $FC) for checksum
lda XRW.FC2Nib,x (4)
wrefd5 ldx #$60 (2) restore slot. warning: modified by prenib
sta IO.D2.WLoad,x (5)
lda IO.D2.WShift,x (4)
ldy #$00 (2) set y = index end mark table.
pha (3) waste another 11 micro-seconds
pla (4)
nop (2)
nop (2)
L58D3 lda XRW.EndDataMark,y (4) dm4, dm5, dm6 and turn off byte.
jsr wnibl (15,6) write it
iny (2)
cpy #$04 (2) have all end marks been written ?
bne L58D3 (3) if not.
clc (2,9)
lda IO.D2.ReadMode,x out of write mode
lda IO.D2.WShift,x to read mode.
rts return from write.
* 7-bit nibl write subroutines
wnibl9 clc (2) 9 cycles, then write.
wnibl7 pha (3) 7 cycles, then write.
pla (4)
wnibl sta IO.D2.WLoad,x (5) nibl write
ora IO.D2.WShift,x (4) clobbers acc, not carry
XRW.Write.RTS rts (6)
*--------------------------------------
* delays a specified number of 100 usec intervals for motor timing.
* on entry: acc holds number of 100 usec intervals to delay.
* on exit: acc = 0, x = 0, y = unchanged, carry set.
* montimel, montimeh are incremented once per 100 usec interval
* for motor on timing.
*--------------------------------------
XRW.WaitSeekTime
* lda #IO.D2.SeekTime
phy
ldy XRW.UnitIndex
lda XRW.D2SeekTime-1,y
ply
.HS 2C BIT ABS
XRW.Wait25600usec
lda #0
XRW.Wait100usecA
phx (3)
.1 ldx #16 (2)
.2 dex (2)
bne .2 (3)
ldx A2L (3)
bit IO.D2.DrvOn,x (4) Slow down ACC boards
inc XRW.montimel (6)
bne .3 (3)
inc XRW.montimeh (6)
.3 sec (2)
sbc #1 (2)
bne .1 (3)
plx (4)
rts (6)
*--------------------------------------
* read subroutine (16-sector format)
*
* reads encoded bytes into nbuf1 and nbuf2.
* first reads nbuf2 high to low, then nbuf1 low to high.
* on entry: x=slot# times $10, read mode
* on exit: carry set if error, else if no error:
* acc=$AA, x=unchanged, y=0, carry clear.
* observe 'no page cross' on some branches !!
*--------------------------------------
XRW.Read txa get slot #
ora #$8C prepare mods to read routine.
sta rd4+1 warning: the read routine is
sta rd5+1 self modified !!
sta rd6+1
sta rd7+1
sta rd8+1
lda buf modify storage addresses also
ldy buf+1
sta ref3+1
sty ref3+2
sec
sbc #$54
bcs L571F branch if no borrow
dey
L571F sta ref2+1
sty ref2+2
sec
sbc #$57
bcs L572B branch if no borrow
dey
L572B sta ref1+1
sty ref1+2
ldy #$20 32 tries to find
L5733 dey
beq L576D branch if can't find data header marks
L5736 lda IO.D2.RData,x
bpl L5736
L573B eor #$D5 1st data mark
bne L5733
nop delay
L5740 lda IO.D2.RData,x
bpl L5740
cmp #$AA 2nd data mark.
bne L573B if not, check for 1st again
nop
L574A lda IO.D2.RData,x
bpl L574A
cmp #$AD 3rd data mark
bne L573B if not, check for data mark 1 again
ldy #$AA
lda #$00
L5757 sta pcl use z-page for keeping checksum
rd4 ldx IO.D2.RData+$60 warning: self modified
bpl rd4
lda XRW.Nib2FC-$96,x
sta nbuf2-$AA,y save the two-bit groups in nbuf.
eor pcl update checksum.
iny next position in nbuf.
bne L5757 loop for all $56 two-bit groups.
ldy #$AA now read directly into user buffer.
bne rd5 always taken.
L576D sec error
rts
ref1 sta $1000,y warning: self modified
rd5 ldx IO.D2.RData+$60 warning: self modified
bpl rd5
eor XRW.Nib2FC-$96,x get actual 6-bit data from dnib table.
ldx nbuf2-$AA,y get associated two-bit pattern
eor dnibl2,x and combine to form whole byte.
iny
bne ref1 loop for $56 bytes.
pha save for now, no time to store...
and #$FC strip low bits.
ldy #$AA prepare for next $56 bytes
rd6 ldx IO.D2.RData+$60 warning: self modified
bpl rd6
eor XRW.Nib2FC-$96,x
ldx nbuf2-$AA,y
eor dnibl3,x
ref2 sta $1000,y warning: self modified
iny
bne rd6 loop unil this group of $56 read
rd7 ldx IO.D2.RData+$60 warning: self modified
bpl rd7
and #$FC
ldy #$AC last group is $54 long
L57A5 eor XRW.Nib2FC-$96,x
ldx nbuf2-$AC,y
eor dnibl4,x combine to form full byte
ref3 sta $1000,y warning: self modified
rd8 ldx IO.D2.RData+$60 warning: self modified
bpl rd8
iny
bne L57A5
and #$FC
eor XRW.Nib2FC-$96,x checksum ok ?
bne L57CC error if not.
ldx A2L test end marks.
L57C2 lda IO.D2.RData,x
bpl L57C2
cmp #$DE
clc
beq L57CD branch if good trailer
L57CC sec
L57CD pla place last byte into user buffer
ldy #$55
sta (buf),y
XRW.Read.RTS rts
*--------------------------------------
XRW.Reset ldx A2L
lda IO.D2.Ph0Off,x
lda IO.D2.Ph1Off,x
lda IO.D2.Ph2Off,x
lda IO.D2.Ph3Off,x
lda IO.D2.ReadMode,x turn off write enable X = slot $S0
rts
*--------------------------------------
* A = target track
*--------------------------------------
XRW.Seek ldx XRW.UnitIndex
pha save target track
jsr XRW.Trk2Qtrk
sta XRW.TargetQTrack
.DO XRWDBG=1
jsr XRW.DEBUG3
.FIN
lda XRW.D2Trk-1,x
jsr XRW.Trk2Qtrk
sta XRW.CurrentQTrack
.DO XRWDBG=1
jsr XRW.DEBUG2
.FIN
pla
sta XRW.D2Trk-1,x will be current track at the end
ldx A2L
ldy A2L
.1 lda XRW.CurrentQTrack
cmp XRW.TargetQTrack
beq .7
bit IO.D2.Ph0Off,x
nop
nop
ldx IO.D2.Ph0Off,y
nop
nop
bcs .2
* Current < Target, must move in
inc
.HS B0 BCS
* Current > Target, must move out
.2 dec
sta XRW.CurrentQTrack
pha
and #6
ora A2L
tay
pla
bcs .3
* Current < Target, must move in
inc
.HS B0 BCS
* Current > Target, must move out
.3 dec
and #6
ora A2L
tax
lda IO.D2.Ph0On,y
nop
nop
lda IO.D2.Ph0On,x
nop
nop
jsr XRW.WaitSeekTime
bra .1
.7 jsr XRW.Wait25600usec
lda IO.D2.Ph0Off,y
nop
nop
lda IO.D2.Ph0Off,x
nop
nop
rts
*--------------------------------------
XRW.Trk2Qtrk asl x2
sta .1+1
bit XRW.D2VolNum-1,x
bpl .1 x4
lsr x3
.1 adc #$ff SELF MODIFIED
rts
*--------------------------------------
XRW.ReadAddr ldy #$FC
sty XRW.CheckSum init nibble counter to $FCFC
ldx A2L get slot #
.1 iny
bne .2 counter LO
inc XRW.CheckSum counter HI
beq .99
.2 lda IO.D2.RData,x read nibl
bpl .2
.3 cmp #$D5 address mark 1 ?
bne .1
nop nibl delay
.4 lda IO.D2.RData,x
bpl .4
cmp #$AA address mark 2 ?
bne .3 if not, is it address mark 1 ?
ldy #$03 index for 4 byte read
.5 lda IO.D2.RData,x
bpl .5
cmp #$96 address mark 3 ?
bne .3 if not, is it address mark 1
sei ???ALREADY DONE by XDOS.devmgr??? no interrupts until address is tested.
lda #$00 init checksum
.6 sta XRW.CheckSum
.7 lda IO.D2.RData,x read 'odd bit' nibl
bpl .7
rol align odd bits, '1' into lsb.
sta XRW.Temp4x4 save them.
.8 lda IO.D2.RData,x read 'even bit' nibl
bpl .8
and XRW.Temp4x4 merge odd and even bits.
sta XRW.AddrField.C,y store data byte.
eor XRW.CheckSum
dey
bpl .6 loop on 4 data bytes.
tay if final checksum non-zero,
bne .99 then error.
.9 lda IO.D2.RData,x
bpl .9
cmp #$DE
bne .99
.10 lda IO.D2.RData,x
bpl .10
cmp #$AA
bne .99
ldy XRW.UnitIndex Successful Read, update Drive table
lda XRW.AddrField.V
sta XRW.D2VolNum-1,y
lda XRW.AddrField.T
sta XRW.D2Trk-1,y and exit with A = Trk
clc normal read ok
rts
.99 sec
rts
*--------------------------------------
.DO XRWDBG=1
XRW.DEBUG phx
ldx #26
lda XRW.AddrField.V
jsr XRW.DEBUG.PRINT
lda XRW.AddrField.T
jsr XRW.DEBUG.PRINT
lda XRW.AddrField.S
jsr XRW.DEBUG.PRINT
inx
lda XRW.ReqTrack
jsr XRW.DEBUG.PRINT
plx
rts
XRW.DEBUG2 phx
ldx #36
bra XRW.DEBUG31
XRW.DEBUG3 phx
ldx #38
XRW.DEBUG31 jsr XRW.DEBUG.PRINT
plx
rts
XRW.DEBUG.PRINT
pha
lsr
lsr
lsr
lsr
jsr .7
pla
and #$0F
.7 ora #$B0
cmp #"9"+1
bcc .8
adc #6
.8 sta $700,x
inx
rts
.FIN
*--------------------------------------
.LIST ON
XRW.FREE .EQ $D540-*
.LIST OFF
.BS $D540-*
*--------------------------------------
* nibl buffer 'nbuf2' must fit in a page
*--------------------------------------
nbuf2 .BS $56 nibl buffer for read/write of low 2-bits of each byte.
*--------------------------------------
* 7-bit to 6-bit 'deniblize' table (16-sector format)
*
* valid codes are $96 to $FF only. codes with more than one pair of
* adjacent zeroes or with no adjacent ones (except bit 7) are excluded.
*
* nibbles in the ranges of $A0-$A3, $C0-$C7, $E0-$E3 are used for
* other tables since no valid nibbles are in these ranges.
* aligned to page boundary + $96
*--------------------------------------
XRW.Nib2FC .HS 0004
* .HS FFFF
XRW.UnitIndex .HS 00
XRW.LastUnitUsed .HS 00
.HS 080C
* .HS FF
XRW.RecalibrateCnt .HS 00
.HS 101418
XRW.XX000000 .HS 008040C0 used in fast prenib as lookup for 2-bit quantities.
* .HS FFFF
XRW.montimel .HS 00
XRW.montimeh .HS 00
.HS 1C20
.HS FFFFFF
.HS 24282C3034
* .HS FFFF
XRW.ReqTrack .HS 00
XRW.ReqSector .HS 00
.HS 383C4044484C
* .HS FF
XRW.BadSeek .HS 00
.HS 5054585C606468
XRW.00XX0000 .HS 00201030 used in fast prenib.
XRW.EndDataMark .HS DEAAEB table using 'unused' nibbles ($C4,$C5,$C6,$C7)
* .HS FFFFFFFF
XRW.AddrField.C .HS 00 AddrField Checksum
XRW.AddrField.S .HS 00 AddrField Sector
XRW.AddrField.T .HS 00 AddrField Track
XRW.AddrField.V .HS 00 AddrField Volume
.HS 6C
.HS FF
*ibstat .HS 00
.HS 707478
.HS FFFFFF
.HS 7C
* .HS FFFF
XRW.Temp4x4 .HS 00
XRW.CheckSum .HS 00 used for address header cksum
.HS 8084
* .HS FF
XRW.RetryCnt .HS 00
.HS 888C9094989CA0
XRW.0000XX00 .HS 0008040C used in fast prenib.
* .HS FF
XRW.CurrentQTrack .HS 00
.HS A4A8AC
* .HS FF
XRW.TargetQTrack .HS 00
.HS B0B4B8BCC0C4C8
.HS FFFF
.HS CCD0D4D8DCE0
.HS FF
.HS E4E8ECF0F4F8FC
*--------------------------------------
* 6-bit to 2-bit conversion tables:
*
* origin = $D600 (page boundary)
*
* dnibl2 abcdef-->0000FE
* dnibl3 abcdef-->0000DC
* dnibl4 abcdef-->0000BA
* page align the following tables:
*--------------------------------------
* FC-bits to nibble conversion table (256 bytes)
*
* codes with more than one pair of adjacent zeroes
* or with no adjacent ones (except B7) are excluded.
*--------------------------------------
dnibl2 .HS 00
dnibl3 .HS 00
dnibl4 .HS 00
XRW.FC2Nib .HS 96
.HS 02000097
.HS 0100009A
.HS 0300009B
.HS 0002009D
.HS 0202009E
.HS 0102009F
.HS 030200A6
.HS 000100A7
.HS 020100AB
.HS 010100AC
.HS 030100AD
.HS 000300AE
.HS 020300AF
.HS 010300B2
.HS 030300B3
.HS 000002B4
.HS 020002B5
.HS 010002B6
.HS 030002B7
.HS 000202B9
.HS 020202BA
.HS 010202BB
.HS 030202BC
.HS 000102BD
.HS 020102BE
.HS 010102BF
.HS 030102CB
.HS 000302CD
.HS 020302CE
.HS 010302CF
.HS 030302D3
.HS 000001D6
.HS 020001D7
.HS 010001D9
.HS 030001DA
.HS 000201DB
.HS 020201DC
.HS 010201DD
.HS 030201DE
.HS 000101DF
.HS 020101E5
.HS 010101E6
.HS 030101E7
.HS 000301E9
.HS 020301EA
.HS 010301EB
.HS 030301EC
.HS 000003ED
.HS 020003EE
.HS 010003EF
.HS 030003F2
.HS 000203F3
.HS 020203F4
.HS 010203F5
.HS 030203F6
.HS 000103F7
.HS 020103F9
.HS 010103FA
.HS 030103FB
.HS 000303FC
.HS 020303FD
.HS 010303FE
.HS 030303FF
*--------------------------------------
XRW.LEN .EQ *-XRW.START
MAN
SAVE usr/src/prodos.fx/prodos.s.xrw
LOAD usr/src/prodos.fx/prodos.s
ASM