Instant Interrupts - Revisited

[Darrel Taylor]

The NEW Elapsed Timer does, ... well .. it does exactly the same thing as the old Elapsed Timer. But now it works with the Instant Interrupt system. Which means that you can use many other interrupts in the same program without much trouble at all. Unlike the last version.

Here's an example of just the Elapsed Timer by itself.

INCLUDE "DT_INTS-14.bas"
INCLUDE "ReEnterPBP.bas"
INCLUDE "Elapsed_INT.bas"  ; Elapsed Timer Routines

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _ClockCount,   PBP,  yes
    endm
    INT_CREATE            ; Creates the interrupt processor

    INT_ENABLE  TMR1_INT  ; Enable Timer 1 Interrupts  
ENDASM

GOSUB ResetTime           ' Reset Time to  0d-00:00:00.00
GOSUB StartTimer          ' Start the Elapsed Timer

Main:
  IF SecondsChanged = 1 THEN  
     SecondsChanged = 0
     LCDOUT $FE,2, DEC Days,"d-",DEC2 Hours,":",DEC2 Minutes,":",DEC2 Seconds
  ENDIF
GOTO Main

Code Size = 537 Words

This will create a Clock counting at 1/100 seconds. It runs in the background of PBP without any other program intervention required.

The time is kept in the variables:

    Ticks    var byte   ' 1/100th of a second
    Seconds  var byte   ' 0-59
    Minutes  var byte   ' 0-59
    Hours    var byte   ' 0-23
    Days     var word   ' 0-65535

The time can be easily displayed with a single line:

    LCDout $FE,2, dec Days,"d-",dec2 Hours,":",dec2 Minutes,":",dec2 Seconds

For each of the variables (Seconds, Minutes, Hours and Days) there is a flag
that indicates when the value of that variable has changed. The Flags are:

SecondsChanged var bit
MinutesChanged var bit
HoursChanged var bit
DaysChanged var bit

If you wanted to display the time like a clock, you could wait until
SecondsChanged = 1, display the time, then reset the flag.

    Loop1:
        if SecondsChanged = 1 then
           LCDout $FE,2, dec Days,"d-",dec2 Hours,":",dec2 Minutes,":",dec2 Seconds
           SecondsChanged = 0
        endif
    Goto Loop1

If you only wanted to display the time each minute instead of every second
just do the same thing using the MinutesChanged flag.

    Loop1:
        if MinutesChanged = 1 then
           LCDout $FE,2, dec Days,"d-",dec2 Hours,":",dec2 Minutes
           MinutesChanged = 0
        endif
    Goto Loop1

The timer can be Stopped and Started, like a stopwatch.

    Gosub StopTimer
    Gosub StartTimer