Interrupt mystery - need some guru help

[xnihilo]

In the code below, something strange happens.
(I'm using an LCD display to check what's happening in the program.)

When the program starts, it seems to jump directly to the On Interrupt routine and when the porta pins states are displayed I see that the values are those I expect:
A.0=1, A.1=1, A.2=1, A.3=0, A.4=1, A.5=1 so no interrupt should have occured because there is absolutely nothing connected to portA.

WHY???

Can someone help me to solve this mystery.

Thanks for any help.














@ 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

'-----------------------------------------
DEFINE LCD_DREG PORTC 'data port out is portc
DEFINE LCD_DBIT 0 'data on portc0-portc3

DEFINE LCD_RSREG PORTC 'rs is on portC5
DEFINE LCD_RSBIT 5

DEFINE LCD_EREG PORTC 'enable in on portC4
DEFINE LCD_EBIT 4

DEFINE LCD_BITS 4 '4bits data bus
DEFINE LCD_LINES 2 '2lines display
DEFINE LCD_COMMANDUS 2000 '2ms cmd delay
DEFINE LCD_DATAUS 50 '50us data delay

CLEAR

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
WPUA = %110111 'enable internal weak pull ups resistors individually on portA pins to bring them HIGH internaly, except for porta.3 (Ra3 can be set as mclr or as i/o port with config words)
INTCON = %10001000 'enable GIE and porta interrupts on change, datasheet p13
IOCA = %111111 'no int for ra4 = r/s bit
TRISA = %111111
TRISC = %000000 'all portc pins are set to output mode, PWM starts if CCP1CON is enabled
'PORTA = %000000 'turn off porta pins
'PORTC = %000000 'turn off portc pins

i VAR BYTE

ON INTERRUPT GOTO in_sig 'when interrupt occurs on any portA pin (except portA.3) go to int routine

loop1: 'main program is a stupid loop waiting for a int on change triggered by an ir signal on sensors

'-----------------
'test
lcdout $fe,2 'home pos
lcdout $fe,1,"loop1" 'clear and display
'-----------------

PAUSEus 15 'shortest pause possible to quickly jump to routine for extracting bullet signal contents
'at 8MHz, minimum delay is 12 uS (or 24 uS at 4MHz)
'in my routine, some uS can be wasted until the signal decoding occurs, too much and the signal will be invalid because of the offset
GOTO loop1

DISABLE
'disable interrupts while executing the interrupt routine (do not put check interrupts calls after each instruction)
in_sig: 'int routine code starts here
'--------------
for i = 0 to 5
LCDOUT $FE, 1,"value",#i,"=",#portA.0(i)
PAUSE 2000
nEXT i

INTCON.0 = 0

resume 'end int routine
enable 'REENABLE interrupts (global flag), PBP lame instruction

END 'end of program

'1. How can I reference a BIT in a BYTE?
'http://www.picbasic.co.uk/forum/archive/index.php/t-544.html
' For MyVar=0 to 7
'MyBit=MyByte.0(MyVar)
'LCDOut $FE,1,"Bit ",#MyVar,"=",#MyBit
'Pause 2000
'Next MyVar

[skimask]

No mystery here...
Re-read the IOC section in the datasheet...
Your answer is there...

[xnihilo]

yes, there are a lot of answers there.
I'm not a programmer so it requires a lot of efforts for me to program. I'm new with PBP and PICs.
It's pretty complicated and I'm tired because I work on my project every night till late so I must be missing the point. So if you know the answer, could you help me please.

[skimask]

I'm not a programmer so it requires a lot of efforts for me to program. I'm new with PBP and PICs.
It's pretty complicated and I'm tired because I work on my project every night till late so I must be missing the point. So if you know the answer, could you help me please.

I'm not a programmer either...just ask anybody around here!
But you're answer really is in the datasheet, DS41202F, Section 4.2.3
And if I tell you, then you will have learned but ONE single thing.
If you figure it out, you'll have begun to understand a number of things...

[xnihilo]

is it because pic sets all ports to input pins upon powerup?

[BobP]

Hi xnihilo,

skimask has pinpointed the passage in the datasheet that clearly tells you what you need to do before enabling the interrupt and after servicing the interrupt. I appreciate that English is probably not your first language but re-examine the paragraph and what it tells you is required before enabling the interrupt?

Regards,
Bob