I modified dt's Elapsed_INT-18.bas file so I could use the "Ticks" as a millisecond counter function (like millis() in arduino C ) it rolls over every 65 seconds but using unsigned integer subtracts its very handy for short interval timing and has no blocking issues . the fairly low interrupt rate minimises effect on normal pgm throughput.

I'm sure Elapsed_INT-14.bas is easily adapted to match , but I have no copy of it




Code:
'***************************************************************************
'*  Name    : Elapsed_INT-18.bas                                           *
'*  Author  : Darrel Taylor                                                *
'*  Date    : JUL 11, 2006 : 7/11/2010                                     *
'*  Version : modified to use ticks useable  as a millisecond   counter                                                      *
'*  Notes   : Must have DT_INTS-18.bas loaded first                        *
'*   ver 1.2: Now works at any OSC frequency without using the prescaler   *
'***************************************************************************
DISABLE DEBUG

; syntax =     Handler  IntSource,        Label, Type, ResetFlag?
DEFINE  Elapsed_Handler  TMR1_INT,  _ClockCount,  asm,  yes
; the above define can be used in the INT_LIST macro, if desired (optional)

Ticks            VAR word   ; Counts timer Overflows
T1Post           VAR BYTE   ; Timer1 postscaler
Seconds          VAR BYTE
Minutes          VAR BYTE
Hours            VAR BYTE
Days             VAR WORD

SecondsChanged   VAR BIT    ; idicates that the value has changed
MinutesChanged   VAR BIT
HoursChanged     VAR BIT
DaysChanged      VAR BIT

GOSUB ResetTime             ; initialize the Elapsed Timer

Goto OverElapsed            ; skip over the routines

' -------------- calc timer reload Constants -------------------------------
ASM
T1PS = 1                             ; start with 1:1 postscaler
TimerConst = ((OSC*1000000)/4/100)   ; how many timer ticks will it take
  while TimerConst > 65400           ; if it's more than the timer can count
T1PS = T1PS * 2                      ;   double the postscaler
TimerConst = TimerConst / 2          ;   halve the count
  endw
TimerConst = 65536 - TimerConst + 6  ; final reload value   !!!!! was 8 but clk runs fast
  
  
; -----------------  ADD TimerConst to TMR1H:TMR1L -------------------------
ADD2_TIMER   macro
    BCF     T1CON,TMR1ON, 0       ;  1 Turn off timer
    MOVLW   LOW(TimerConst)       ;  1
    ADDWF   TMR1L,F, 0            ;  1    
    BTFSC   STATUS,C              ;  1/2
    INCF    TMR1H,F, 0            ;  1
    MOVLW   HIGH(TimerConst)      ;  1
    ADDWF   TMR1H,F, 0            ;  1
    endm

; -----------------  ADD TimerConst to TMR1H:TMR1L and restart TIMER1 ------
RELOAD_TIMER  macro
    ADD2_TIMER
    BSF     T1CON,TMR1ON, 0       ;  1   Turn TIMER1 back on  (8 cycles)
    endm

; -----------------  Load TimerConst into TMR1H:TMR1L ----------------------
LOAD_TIMER  macro
    MOVE?CT  0, T1CON,TMR1ON
    MOVE?CB  0, TMR1L
    MOVE?CB  0, TMR1H
    ADD2_TIMER
    endm
ENDASM

' ------[ This is the Interrupt Handler ]-----------------------------------
T1PS  CON EXT
ClockCount:
@ RELOAD_TIMER                   ; Reload TIMER1

    T1Post = T1Post + 1
   
    IF T1Post = T1PS THEN
  
     T1Post = 0
    
    Ticks = Ticks + 1
      
       IF Ticks //100 ==0 THEN
      
'          Ticks = 0           Seconds = Seconds + 1
           SecondsChanged = 1
           IF Seconds = 60 THEN
              Seconds = 0
              Minutes = Minutes + 1
              MinutesChanged = 1
           ENDIF
           IF Minutes = 60 THEN
              Minutes = 0
              Hours = Hours + 1
              HoursChanged = 1
           ENDIF
           IF Hours = 24 THEN
              Days = Days + 1
              DaysChanged = 1
              Hours = 0
           ENDIF
       ENDIF
    ENDIF
@ INT_RETURN                     ; Restore context and return from interrupt

'-----====[ END OF TMR1 Interrupt Handler ]====-----------------------------

StartTimer:
    T1CON = 1                    ; 1:1, FOSC4, TMR1ON
RETURN

; --------------------------------------------------------------------------
StopTimer:
    T1CON.0 = 0                  ; Turn OFF Timer1
RETURN

; --------------------------------------------------------------------------
BitSave  VAR  BIT

ResetTime:
    BitSave = T1CON.0            ; Save TMR1ON bit
@   LOAD_TIMER                   ; Load TimerConst
    T1CON.0 = BitSave            ; Restore TMR1ON bit
    T1Post = 0                   ; clear the postscaler
    Ticks = 0
    Seconds = 0
    Minutes = 0
    Hours = 0
    Days = 0
    SecondsChanged = 1           ; indicate everything has changed
    MinutesChanged = 1           ; so that 00:00:00 is processed
    HoursChanged = 1
    DaysChanged = 1
RETURN


OverElapsed:
ENABLE DEBUG