Math operations & Syntax?

[kevj]

I'm a bit confused on the actual use and syntax when using WORD sized variables.

I'm going to measure a timed event, then use that time as a basis for a pass/fail trial of another timed event. I need to measure the time (16-bit), then manipulate it (subtract a few microseconds), then use that manipulated result to continually pre-load the timer and see if the event happens again within the similar allotted time frame.


Here is what I plan to do and how I will syntax it - wanted to see if I'm doing this correctly?

Using TMR1 ...

'Variables
'-------------
tMeasure VAR WORD   'Holder for the time
tResult VAR WORD      'Holder for modified time
tSet VAR WORD	    'Holder for timer set value


'Measure event, manipulate Data
'-------------
T1CON.0=0           'Stop timer
   TMR1H = %00000000   'Reset the timer
   TMR1L = %00000000    '......
   PIR1.0=0            'Clear timer overflow bit
   T1CON.0=1           'Start timer

        ''' Wait for event to measure

   T1CON.0=0     'Stop Timer

tMeasure = TMR1   		'Should put timer stop value into tMeasure
tResult = tMeasure - 100 	'Subtract 100 cycles
tSet = 65025 - tResult          'Setpoint for timer

        '' If I pre-load the timer with this tSet number, then wait
        '' for it to time out, it should run for a time period in cycles
        '' equal to tResult - right?


'Perform trial timeout
'--------------------
   T1CON.0=0           'Stop timer
   TMR1 = tSet
   PIR1.0=0            'Clear timer overflow bit
   T1CON.0=1           'Start timer
   WHILE PIR1.0=0 : WEND
   TOGGLE probe     'Should happen about tResult cycles after 
                          'starting the timer, yes?

'

My real questions are with the manipulation of the 16-bit variables. When I write "TMR1 = tSet", the TMR1H and TMR1L registers are filled correctly with the high byte and low byte of tSet - correct?

Normally I would set TMR1 by manually setting the TMR1H and TMR1L with binary code like "TMR1H = %11101100".

Also, do I need to worry about which direction the data is justified? I know it's important, but if I do it as written, is PBP smart enough to get the justification correct for me?


Thank you!