********************************************************************
* Clock - OS-9 Level One V2 Clock module
*
* $Id$
*
* NOTE:  This clock is TOTALLY VALID for ALL DATES between 1900-2155
*
* Ed.    Comments                                       Who YY/MM/DD
* ------------------------------------------------------------------
*   5    From Tandy OS-9 Level One VR 02.00.00
*   6    Modified to handle leap years properly for     BGP 99/05/03
*        1900 and 2100 A.D.

         nam   Clock
         ttl   OS-9 Level One V2 Clock module

         ifp1
         use   defsfile
         endc

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

         mod   eom,name,tylg,atrv,ClkEnt,size

size     equ   .

name     fcs   /Clock/
         fcb   edition

SysTbl   fcb   F$Time
         fdb   FTime-*-2
         fcb   F$VIRQ
         fdb   FVIRQ-*-2
         fcb   $80

* table of days of the month
MonthChk fcb   00
         fcb   31                      January
         fcb   28                      February
         fcb   31                      March
         fcb   30                      April
         fcb   31                      May
         fcb   30                      June
         fcb   31                      July
         fcb   31                      August
         fcb   30                      September
         fcb   31                      October
         fcb   30                      November
         fcb   31                      December

ClockIRQ clra
         tfr   a,dp                    set direct page to zero
         lda   PIA.U4+3               get hw byte
         bmi   L0032                   branch if sync flag on
         jmp   [>D.SvcIRQ]
L0032    lda   PIA.U4+2               clear interrupt?
         dec   <D.Tick                 decrement tick counter
         bne   L007F                   go around if not zero
         ldd   <D.Min                  get minutes/seconds
* Seconds increment
         incb                          increment seconds
         cmpb  #60                     full minute?
         bcs   L0079                   nope...
* Minutes increment
         inca                          else increment minute
         cmpa  #60                     full hour?
         bcs   L0078                   nope...
         ldd   <D.Day                  else increment day
* Hour increment
         incb                          increment hour
         cmpb  #24                     past 23rd hour?
         bcs   L0075                   branch if not
* Day increment
         inca                          else increment day
         leax  >MonthChk,pcr
         ldb   <D.Month
*         cmpb  #3                      is this February?
*         bne   L005F
*         ldb   <D.Year                 check year
*         beq   L005F                   if century, it's a leap year
*         andb  #$03                    leap year? (divisible by 4)
*         beq   L0060                   nope
*L005F    inca
*L0060    ldb   <D.Month                get month
         cmpa  b,x                     compare days to max days
         bls   L0074                   branch if ok
         cmpb  #2                      is this February?
         bne   L006X                   if not, go on to year/month
* Leap year cases checked here
         ldb   <D.Year                 else check for leap year cases
         beq   L006X                   branch if year 1900
         cmpb  #200                    is it 1900+200 (2100)?
         beq   L006X                   if so, branch
         andb  #$03                    see if 2^4 bit set (leap year)
         cmpd  #$1D00                  29th on leap year?
         beq   L0074                   it's a leap year...
L006X    ldd   <D.Year                 else get year and month
* Month increment
         incb                          increment month
         cmpb  #13                     past December?
         bcs   L0070                   branch if not
* Year increment
         inca                          else in year
         ldb   #1                      and start month in January
L0070    std   <D.Year                 update year/month
         lda   #1                      new month, first day
L0074    clrb                          hour 0
L0075    std   <D.Day                  update day/hour
         clra                          0 minutes
L0078    clrb                          0 seconds
L0079    std   <D.Min                  update min/sec
         lda   <D.TSec
         sta   <D.Tick
L007F    clra
         pshs  a
         ldy   <D.CLTB
         bra   L009E
L0087    ldd   ,x
         subd  #$0001
         bne   L009C
         lda   #$01
         sta   ,s
         lda   $04,x
         beq   L00B8
L0096    ora   #$01
         sta   $04,x
         ldd   $02,x
L009C    std   ,x
L009E    ldx   ,y++
         bne   L0087
         lda   ,s+
         beq   L00B4
         ldx   <D.Proc
         beq   L00AE
         tst   P$State,x
         bpl   L00BC                   branch if sysstate not set
L00AE    jsr   [>D.Poll]
         bcc   L00AE
L00B4    jmp   [>D.AltIRQ]
L00B8    bsr   L00DD
         bra   L0096
L00BC    leay  >L00C4,pcr
         jmp   [>D.URtoSs]
L00C4    jsr   [>D.Poll]
         bcc   L00C4
         ldx   <D.Proc
         ldb   P$State,x
         andb  #^SysState              turn off sysstate bit
         stb   P$State,x
         ldd   <P$SWI2,x
         std   <D.SWI2
         ldd   <D.UsrIRQ
         std   <D.SvcIRQ
         bra   L00B4
L00DD    pshs  y,x
L00DF    ldx   ,y++
         stx   -$04,y
         bne   L00DF
         puls  y,x
         leay  -2,y
         rts

FVIRQ    pshs  cc
         orcc  #FIRQMask+IRQMask
         ldy   <D.CLTB
         ldx   <D.Init
         ldb   PollCnt,x
         ldx   R$X,u
         beq   L0118
         tst   ,y
         beq   L010C
         subb  #$02
         lslb
         leay  b,y
         tst   ,y
         bne   L0128
L0106    tst   ,--y
         beq   L0106
         leay  $02,y
L010C    ldx   R$Y,u
         stx   ,y
         ldy   R$D,u
         sty   ,x
         bra   L0124
L0118    leax  R$Y,u
L011A    tst   ,y
         beq   L0124
         cmpx  ,y++
         bne   L011A
         bsr   L00DD
L0124    puls  cc
         clrb
         rts
L0128    puls  cc
         comb
         ldb   #E$Poll
         rts

ClkEnt   equ   *
         pshs  dp,cc
         clra
         tfr   a,dp

         lda   #TPS

         sta   <D.TSec
         sta   <D.Tick

         lda   #TPS/10

         sta   <D.TSlice
         sta   <D.Slice
         orcc  #FIRQMask+IRQMask       mask ints
         leax  >ClockIRQ,pcr
         stx   <D.IRQ
* install system calls
         leay  >SysTbl,pcr
         os9   F$SSvc
         ldx   #PIA.U4
         clra
         sta   1,x                     change PIA.U4 side A to DDR
         sta   ,x                      clear PIA.U4 side A
         sta   3,x                     change PIA.U4 side B to DDR
         coma                          complement A side A
         sta   2,x                     write all 1's to PIA.U4 side B
         lda   #$34
         sta   1,x                     PIA.U4 side A to I/O reg
         lda   #$3F
         sta   3,x                     PIA.U4 side B to I/O reg
         lda   2,x
         puls  pc,dp,cc

* F$Time system call code
FTime    ldx   R$X,u
         ldd   <D.Year
         std   ,x
         ldd   <D.Day
         std   2,x
         ldd   <D.Min
         std   4,x
         clrb
         rts

         emod
eom      equ   *
         end