pulsin: how is it used

[xnihilo]

Hello,

I would like to use pulsin to record the length of a positive pulse, thus I would use

pulsin trigger,1,pulse_length

if trigger is a pin name and pulse_length is a word variable

As I don't know when the trigger will happen, can I jump to the pulsin when I detect a low to high change on a pin (using a polling loop or an interrupt) or is PULSIN expecting to see the rising edge.
As I understand it from the manual, it will record the pulse even if already on and will stop recording once the pin goes low, it it right?

I don't know if my question is clear enough?

'*******************************************************************************
'preset the pic specs and config words at chip programming time
@        device  pic16F684, intrc_osc_noclkout, BOD_OFF, PWRT_OFF, wdt_off, mclr_off, protect_off
'*******************************************************************************


'*******************************************************************************
DEFINE OSC 8			'set OSC value to 8MHz for instructions PAUSE, PAUSEus and SOUND
'*******************************************************************************

'*******************************************************************************
'VARIABLES declaration
'IF VARIABLES USED FOUR COUNTER GO OVER 256, USE WORD INSTEAD

pulse_length var word
'*******************************************************************************


CLEAR                     'clears all data ram (128 bytes) and initialize variables (this should however be done in software)

INTCON = 0              'disable interrupts and reset int flags
IOCA = %000000

'*******************************************************************************
'PWM (single output mode) related registers for porta.5.
'PWM is not used. We use normal output on C5.

T2CON = %00000000			'value:4, 1:1 postscale (unused), Timer2 is OFF, Timer 2 Clock prescaler = 1
PR2 = %00110001			'value: 49, PWM Period: 40.0KHz
CCP1CON = %00000000		'capture/compare/PWM module OFF, no pwm signal on portc.5 at this time
CCPR1L = %00001111		'value: 15, PWM Duty Cycle 8 MSB of 10 bits (2 LSB in bits 5 and 4 of CCP1CON), total: 60d
'*******************************************************************************


'*******************************************************************************
'Setting registers

OSCCON = %01110001
CMCON0 =  %00000111			'comparators OFF, val = 7
ANSEL = %00000000			'choose digital i/o, val = 0
OPTION_REG = %01111111 			'enable porta weak pullups (no weak pull-up available for porta.3), p12
'*******************************************************************************


'*******************************************************************************
'Setting ports states, direction and internal weak pull-ups
'USE 10K WPU on RA3 if used as input !!!

TRISA = %000001 				'set porta pins directions (1=input, high impedance),portA.3 is always input pin (datasheet p5)
TRISC = %000000
'use 10K WPU on A3                              
WPUA =  %000000 			

PORTA = %000000 			'set port pins logic, A0 will be a default LOW with 100K WPD
PORTC = %000000 			'set port pins logic
'*******************************************************************************
'*******************************************************************************
'aliasing pins

Symbol trigger = PORTA.0
SYMBOL led = PORTC.3
'*******************************************************************************

PAUSE 3000             'let the power level stabilize if not already done

'flashes at 5Hz
for i = 0 to 4
    High led
    PAUSE 100
    LOW led
    PAUSE 100
NEXT i

PAUSE 2000

start:

While (trigger == 0) : WEND        'while pin is low (no pulse on pin)

'a pulse has been detected (at this step the rising edge is over, the pin is high)
PULSIN trigger,1,pulse_length   '16 bits

WRITE 0,pulse_length.lowbyte
WRITE 1,pulse_length.highbyte

'flash when recording occured and finished (max 327ms with 8MHz 5 us resolution 65536 increments)
HIGH led
PAUSE 2000
LOW led

goto start

END                     'end of program