********************************************************************
* JoyDrv - Joystick Driver for 6551/Logitech Mouse
*
* $Id$
*
* Ed.    Comments                                       Who YY/MM/DD
* ------------------------------------------------------------------
* 6      L2 Upgrade distribution version

         nam   JoyDrv
         ttl   Joystick Driver for 6551/Logitech Mouse

* Disassembled 98/09/09 09:22:44 by Disasm v1.6 (C) 1988 by RML

         ifp1  
         use   defsfile
         use   l51.defs
         endc  

tylg     set   Systm+Objct
atrv     set   ReEnt+rev
rev      set   $01
edition  set   6

MPISlot  set   $00

         mod   eom,name,tylg,atrv,start,$FF68

name     fcs   /JoyDrv/
         fcb   edition

SlotSlct equ   MPISlot

start    lbra  Init
         lbra  Term
         lbra  SSMsBtn
         lbra  SSMsXY
         lbra  SSJoyBtn

SSJoyXY  pshs  x,b,a
         ldx   #PIA0Base
         lda   <$23,x
         ldb   <$20,x
         pshs  b,a
         anda  #$F7
         sta   <$23,x
         lda   $01,x
         ldb   $03,x
         pshs  b,a
         andb  #$F7
         lsr   $04,s
         bcs   L0043
         orb   #$08
L0043    stb   $03,x
         lda   ,s
         ora   #$08
         bsr   L0065
         std   $06,s
         lda   ,s
         anda  #$F7
         bsr   L0065
         std   $04,s
         puls  b,a
         sta   $01,x
         stb   $03,x
         puls  b,a
         stb   <$20,x
         sta   <$23,x
         puls  pc,y,x
L0065    sta   $01,x
         lda   #$7F
         ldb   #$40
         bra   L0078
L006D    lsrb  
         cmpb  #$01
         bhi   L0078
         lsra  
         lsra  
         tfr   a,b
         clra  
         rts   
L0078    pshs  b
         sta   <$20,x
         tst   ,x
         bpl   L0085
         adda  ,s+
         bra   L006D
L0085    suba  ,s+
         bra   L006D

IRQPckt  equ   *
Pkt.Flip fcb   Stat.Flp   D.Poll flip byte
Pkt.Mask fcb   Stat.Msk   D.Poll mask byte
         fcb   $01        priority

Init     clra
         clrb 
         sta   Btn.Cntr,u set up Rx data sync, no button(s) pressed
         std   CrntXPos,u set up X position at left screen edge
         ldd   #HResMaxY*2
         std   CrntYPos,u set up Y position at top screen edge
         ldd   M$Mem,pcr get base hardware address
         addd  #StatReg   status register address
         leax  IRQPckt,pcr
         leay  IRQSvc,pcr
         os9   F$IRQ
         bcs   InitExit   go report error...
         ldx   M$Mem,pcr get base hardware address again
         ldd   #(TIC.RTS!Cmd.DTR)*256+(DB.8!Ctl.RClk!BR.01200) [D]=command:control
         pshs  cc
         orcc  #IntMasks  disable IRQs while setting up hardware
         sta   PRstReg,x  reset 6551
         std   CmdReg,x   set command and control registers
         lda   >PIA1Base+3 get PIA CART* input control register
         anda  #$FC       clear PIA CART* control bits
         sta   >PIA1Base+3 disable PIA CART* FIRQs
         lda   >PIA1Base+2 clear possible pending PIA CART* FIRQ
         lda   #$01       GIME CART* IRQ enable
         ora   <D.IRQER   mask in current GIME IRQ enables
         sta   <D.IRQER   save GIME CART* IRQ enable shadow register
         sta   >IrqEnR    enable GIME CART* IRQs
         ldb   DataReg,x  *ensure old error,
         ldb   StatReg,x  *Rx data, and
         ldb   DataReg,x  *IRQ flags
         ldb   StatReg,x  *are clear
         andb  Pkt.Mask,pcr IRQ bits still set?
         bne   InitErr    yes, go disable ACIA and return...
         lda   SlotSlct,pcr get MPI slot select value
         bmi   InitExit   no MPI slot select, go exit...
         sta   >MPI.Slct  set MPI slot select register
         puls  pc,cc recover original regs, return...

Term     pshs  cc         save regs we alter
         orcc  #IntMasks  mask IRQs while disabling ACIA
InitErr  ldx   M$Mem,pcr  get base address
         lda   #TIC.RTS!Cmd.RxIE!Cmd.DTR *disable all
         sta   CmdReg,x   *ACIA IRQs
         puls  cc
         leax  StatReg,x  point to status register
         tfr   x,d        copy status register address
         ldx   #$0000     remove IRQ table entry
         leay  IRQSvc,pcr
         os9   F$IRQ
InitExit rts

SSJoyBtn ldb   #$FF
         ldx   #PIA0Base
         stb   $02,x
         ldb   ,x
         comb  
         andb  #$0F
         rts   

SSMsBtn  pshs  cc
         orcc  #IntMasks
         lda   ,u
         tfr   a,b
         andb  #$C0
         bne   L0120
         bita  #$20
         beq   L011A
         orb   #$03
L011A    bita  #$10
         beq   L0120
         orb   #$0C
L0120    anda  #$3F
         sta   ,u
         puls  pc,cc

SSMsXY   ldd   #$017E
         pshs  cc
         orcc  #IntMasks
         ldx   CrntXPos,u
         subd  CrntYPos,u
         lsra  
         rorb  
         tfr   d,y
         puls  pc,cc

***
* Mouse IRQ service routine.
*
* INPUT:  A = flipped and masked device status byte
*         U = mouse data area address
*
* OUTPUT:  updated serial mouse data
*          CC Carry clear
*          D, X, Y, and U registers may be altered
*
* ERROR OUTPUT:  none
IRQSvc   ldx   M$Mem,pcr
         bita  #Stat.Err  any error(s)?
         beq   ChkRDRF    no, go check Rx data
         ldb   DataReg,x  read Rx data register to clear error flags
ClrRxCnt lda   Btn.Cntr,u get current button status and Rx data counter
         anda  #^BC.RxCnt clear Rx data counter
ButnExit sta   Btn.Cntr,u reset Rx mouse data counter to wait for sync...
IRQExit  clrb             clear Carry to mark IRQ serviced
         rts   

ChkRDRF  bita  #Stat.RxF  Rx data?
         beq   IRQExit    no, but this branch should never be taken...
         ldb   DataReg,x  get Rx data
         lda   Btn.Cntr,u get button status and Rx counter
         anda  #BC.RxCnt  waiting for sync with mouse data?
         bne   ChkOfst    no, go check Rx offset...
         tfr   b,a        copy Rx data
         anda  #SyncMask  clear button status bits
         cmpa  #SyncData  is it *PROBABLY* the initial (sync) byte?
         bne   IRQExit    no, just ignore it...
         comb             invert button bits to match SS.Mouse format
         lslb             *move button
         lslb             *status into
         lslb             *bits 5-3
         andb  #BC.Butns  clear everything but the button bits
         incb             set Rx counter to first XY position byte
         pshs  b
         lda   ,u
         bita  #$08
         beq   L017A
         bitb  #$08
         bne   L017A
         lda   #$C0
         ldx   CrntXPos,u
         cmpx  #$0140
         bcs   L017A
         lsla
L017A    anda  #$C0
         ora   ,s+
         bra   ButnExit   go save new button status and Rx counter, exit...
ChkOfst  cmpa  #PcktSize-1 last byte in mouse packet?
         bcs   SaveData   no, go save mouse data to Rx buffer...
         ldx   #HResMaxY*2 get maximum Y position
         pshs  x          save it for CalcPos subroutine
         leax  CrntYPos,u point to current Y position
         leay  Buffer+1,u point to primary Y offset
         bsr   CalcPos    go calculate & save mouse's new Y position
         ldb   Buffer+2,u get mouse packet's secondary X offset
         ldx   #HResMaxX  get maximum X position
         stx   ,s         save it for CalcPos subroutine
         leax  CrntXPos,u point to current X position
         leay  Buffer+0,u point to primary X offset
         bsr   CalcPos    go calculate & save mouse's new X position
         leas  2,s        clean up stack
         bra   ClrRxCnt   go save button status and clear Rx counter, exit...
SaveData stb   a,u        save XY position byte to mouse data Rx buffer
         inc   Btn.Cntr,u point to next byte in Rx buffer
         clrb             clear Carry to mark IRQ serviced
         rts   

CalcPos  sex              sign extend mouse packet's 2nd XY offset ([D] = -128 to +127)
         pshs  d          save it temporarily...
         ldb   ,y         get mouse packet's 1st XY offset
         sex              sign extend it ([D] = -128 to +127)
         addd  ,s         add mouse's 2nd XY offset
         std   ,s         save XY offset total temporarily...
         bpl   PosAdjst   go de-sensitize positive "ballistic" XY offset...
         orb   #%00000111 if -8<XYoffset<0, no "ballistic" response
         addd  #1         "fix" negative offset "ballistic" response
         bra   RShiftD    go calculate "ballistic" offset...
PosAdjst andb  #%11111000 if 0<XYoffset<8, no "ballistic" response
RShiftD  asra             *calculate 50% of XY offset
         rorb             *for "ballistic" response
         addd  ,s++       add original XY offset total, clean up stack
         addd  ,x         add mouse's current XY position
         bpl   CheckPos   zero or positive XY position, go check it...
         clra             *set minimum
         clrb             *XY position
CheckPos cmpd  2,s        past maximum XY position?
         bls   SavePos    no, go save it...
         ldd   2,s        get maximum XY position
SavePos  std   ,x         save new XY position
         rts   

         emod  
eom      equ   *
         end