Greetings Richard,

that makes total sense, sorry for that.

Here is the code being used to test/troubleshoot the issue...

The sending PIC triggers COM pin high/low before sending the data.
The receiving PIC detects the COM trigger with IOC interrupt and starts listening.
This part of the code is working since it's detecting the trigger and starts listening.
The thing that is not working is the data reception correctly.

Send pic code
Code:
'****************************************************************'*  Name    : 16F1508_Send.PBP                                  *
'*            PORTA.2 CONNECTED TO PORTA.1 ON RECEIVING PIC     *
'****************************************************************
'
;----[16F1508 Hardware Configuration]-------------------------------------------
#IF __PROCESSOR__ = "16F1508"
  #DEFINE MCU_FOUND 1
#CONFIG
cfg1 = _FOSC_INTOSC           ; INTOSC oscillator: I/O function on CLKIN pin
cfg1&= _WDTE_OFF              ; WDT disabled
cfg1&= _PWRTE_OFF             ; PWRT disabled
cfg1&= _MCLRE_OFF             ; MCLR/VPP pin function is digital input
cfg1&= _CP_OFF                ; Program memory code protection is disabled
cfg1&= _BOREN_OFF             ; Brown-out Reset disabled
cfg1&= _CLKOUTEN_OFF          ; CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin
cfg1&= _IESO_OFF              ; Internal/External Switchover Mode is disabled
cfg1&= _FCMEN_OFF             ; Fail-Safe Clock Monitor is disabled
  __CONFIG _CONFIG1, cfg1


cfg2 = _WRT_OFF               ; Write protection off
cfg2&= _STVREN_OFF            ; Stack Overflow or Underflow will not cause a Reset
cfg2&= _BORV_LO               ; Brown-out Reset Voltage (Vbor), low trip point selected.
cfg2&= _LPBOR_OFF             ; Low-Power BOR is disabled
cfg2&= _LVP_OFF               ; High-voltage on MCLR/VPP must be used for programming
  __CONFIG _CONFIG2, cfg2


#ENDCONFIG


#ENDIF


;----[Verify Configs have been specified for Selected Processor]----------------
;       Note: Only include this routine once, after all #CONFIG blocks
#IFNDEF MCU_FOUND
  #ERROR "No CONFIGs found for [" + __PROCESSOR__ +"]"
#




DEFINE OSC 16                               ' Let PBP clock speed will be 16MHz
OSCCON = %01111011                          ' Use internal oscillator and set to 16MHz


OPTION_REG.7 = 0                            ' Enable individual control of weak pull-ups
WPUA.0 = 0                                  ' Disable weak pull-up on RA0
WPUA.1 = 0                                  ' Disable weak pull-up on RA1
WPUA.2 = 0                                  ' Disable weak pull-up on RA2
WPUA.3 = 0                                  ' Disable weak pull-up on RA3
WPUA.4 = 1                                  ' Enable weak pull-up on RA4
WPUA.5 = 1                                  ' Enable weak pull-up on RA5


DACCON0.7 = 0                               ' Disable DAC
CM1CON0.7 = 0                               ' Disable comparator 1
CM2CON0.7 = 0                               ' Disable comparator 2


TRISA = %00000000                          
TRISB = %00000000 
TRISC = %00000000      


'*****************************************************************************


INCLUDE "ALLDIGITAL.pbp"
DEFINE SHOWDIGITAL 1


INCLUDE "modedefs.bas" 


DEFINE DEBUG_REG PORTA 			' Set Debug pin port
DEFINE DEBUG_BIT 2				' Set Debug pin bit
DEFINE DEBUG_BAUD 2400			' Set Debug baud rate 
DEFINE DEBUG_MODE 0				' Set Debug mode: 0 = true, 1 = inverted


'*****************************************************************************
'PORTS & PINS 


COMMTX	    	VAR		PORTA.2	
MESLED	    	VAR		PORTB.5		'MESSAGE LED


PreAmble 		CON 	$A5    


'*****************************************************************************
INIT:


PORTA=%00000000
PORTB=%00000000
PORTC=%00000000


GOTO START


'*****************************************************************************
START:


HIGH INTLED
HIGH COMMTX
PAUSE 500
LOW COMMTX
LOW INTLED


PAUSE 200


HIGH MESLED


debug PreAmble,$af,$c2,$b5,$ef,13,10


PAUSE 500
LOW MESLED


PAUSE 4000


GOTO START


'------------------------------------------------------------------------------

Receive pic code
Code:
'****************************************************************'*  Name    : 16F1503_Receive.PBP                               *
'*            PORTA.1 CONNECTED TO PORTA.2 ON SENDING PIC       *
'****************************************************************
'
;----[16F1503 Hardware Configuration]-------------------------------------------
#IF __PROCESSOR__ = "16F1503"
  #DEFINE MCU_FOUND 1
#CONFIG
cfg1 = _FOSC_INTOSC           ; INTOSC oscillator: I/O function on CLKIN pin
cfg1&= _WDTE_OFF              ; WDT disabled
cfg1&= _PWRTE_OFF             ; PWRT disabled
cfg1&= _MCLRE_OFF             ; MCLR/VPP pin function is digital input
cfg1&= _CP_OFF                ; Program memory code protection is disabled
cfg1&= _BOREN_OFF             ; Brown-out Reset disabled
cfg1&= _CLKOUTEN_OFF          ; CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin
  __CONFIG _CONFIG1, cfg1


cfg2 = _WRT_OFF               ; Write protection off
cfg2&= _STVREN_OFF            ; Stack Overflow or Underflow will not cause a Reset
cfg2&= _BORV_LO               ; Brown-out Reset Voltage (Vbor), low trip point selected.
cfg2&= _LPBOR_OFF             ; Low-Power BOR is disabled
cfg2&= _LVP_OFF               ; High-voltage on MCLR/VPP must be used for programming
  __CONFIG _CONFIG2, cfg2


#ENDCONFIG


#ENDIF


;----[Verify Configs have been specified for Selected Processor]----------------
;       Note: Only include this routine once, after all #CONFIG blocks
#IFNDEF MCU_FOUND
  #ERROR "No CONFIGs found for [" + __PROCESSOR__ +"]"
#ENDIF


'*****************************************************************************


DEFINE OSC 16                               ' Let PBP clock speed will be 16MHz
OSCCON = %01111011                          ' Use internal oscillator and set to 16MHz


OPTION_REG.7 = 0                            ' Enable individual control of weak pull-ups
WPUA.0 = 0                                  ' Disable weak pull-up on RA0
WPUA.1 = 0                                  ' Disable weak pull-up on RA1
WPUA.2 = 0                                  ' Disable weak pull-up on RA2
WPUA.3 = 0                                  ' Disable weak pull-up on RA3
WPUA.4 = 0                                  ' Disable weak pull-up on RA4
WPUA.5 = 0                                  ' Disable weak pull-up on RA5


DACCON0.7 = 0                               ' Disable DAC
CM1CON0.7 = 0                               ' Disable comparator 1
CM2CON0.7 = 0                               ' Disable comparator 2


TRISA = %00001010                           ' Set RA1-RA3 as inputs
TRISC = %00000000                           ' Set RC port as output


'*****************************************************************************


INCLUDE "ALLDIGITAL.pbp"
DEFINE SHOWDIGITAL 1


INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts


INCLUDE "modedefs.bas" 


DEFINE DEBUG_REG PORTA 			' Set Debug pin port
DEFINE DEBUG_BIT 3				' Set Debug pin bit
DEFINE DEBUG_BAUD 2400			' Set Debug baud rate 
DEFINE DEBUG_MODE 0				' Set Debug mode: 0 = true, 1 = inverted


DEFINE DEBUGIN_REG PORTA		' Set Debugin pin port 
DEFINE DEBUGIN_BIT 1			' Set Debugin pin bit  
DEFINE DEBUGIN_BAUD 2400		' Set Debugin baud rate (same as Debug baud) 
DEFINE DEBUGIN_MODE 0			' Set Debugin mode: 0 = true, 1 = inverted  


'*****************************************************************************
;____[ For 12F/16F only - Interrupt Context save locations]_________________
;-- Place a copy of these variables in your Main program -------------------
;--   The compiler will tell you which lines to un-comment                --
;--   Do Not un-comment these lines                                       --
;---------------------------------------------------------------------------
;wsave   VAR BYTE    $20     SYSTEM      ' location for W if in bank0
;wsave   VAR BYTE    $70     SYSTEM      ' alternate save location for W 
                                         ' if using $70, comment wsave1-3


' --- IF any of these three lines cause an error ?? ------------------------
'       Comment them out to fix the problem ----
' -- Which variables are needed, depends on the Chip you are using -- 
;wsave1  VAR BYTE    $A0     SYSTEM      ' location for W if in bank1
;wsave2  VAR BYTE    $120    SYSTEM      ' location for W if in bank2
;wsave3  VAR BYTE    $1A0    SYSTEM      ' location for W if in bank3
' --------------------------------------------------------------------------
'https://www.picbasic.co.uk/forum/showthread.php/3251-Instant-Interrupts-Revisited/page7?highlight=DT%27s+instant+interrupts
'https://www.picbasic.co.uk/forum/showthread.php/3251-Instant-Interrupts-Revisited/page16?highlight=DT%27s+instant+interrupts
'Open the DT_INTS-14.bas file and comment out the wsave lines. 
'The 675 doesn't have any usable RAM in banks 1,2 or 3


'*****************************************************************************


INTCON.3=1
IOCAP.1=1 	     'POSITIVE EDGE @ A1 ON
IOCAN=%0		 'NEGATIVE EDGE OFF


'page 106


'*****************************************************************************
'---[INT - interrupt handler]---------------------------------------------------
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler  IOC_INT,    _IOCinterrupts,    PBP,  yes
endm
INT_CREATE               ; Creates the interrupt processor
ENDASM


@ INT_ENABLE IOC_INT


'*****************************************************************************
'PORTS & PINS 
	
INTLED	    VAR		PORTC.3		'INTERRUPT LED		
MESLED	    VAR		PORTC.4		'MESSAGE LED


'*****************************************************************************


DAT1        VAR     BYTE	'
DAT2        VAR     BYTE	'
DAT3        VAR     BYTE	'
CT			VAR		BYTE	'


'*****************************************************************************
INIT:


PORTC=%000000


GOTO START


'------------------------------------------------------------------------------
START:


LOW INTLED
LOW MESLED


GOTO START


'------------------------------------------------------------------------------
IOCinterrupts:


@   INT_DISABLE IOC_INT 


HIGH INTLED


PAUSE 500


DEBUGIN 1000,timeoutlabel,[WAIT($af),DAT1,DAT2,DAT3]


PAUSE 200


pause 500


low INTLED


PAUSE 500


IF DAT1=$c2 THEN
GOTO PROGSEL
ENDIF


'RETURN TO PROGRAM
IOCAF=%0
@ INT_ENABLE IOC_INT
@ INT_RETURN


;-------------------------------------------------------------------------------
timeoutlabel:


low INTLED


HIGH MESLED
debug DEC 99,DAT1,DAT2,DAT3,13,10 'Message confirming bad reception


pause 1000
low MESLED


'RETURN TO PROGRAM
IOCAF=%0
@ INT_ENABLE IOC_INT
@ INT_RETURN


;-------------------------------------------------------------------------------
PROGSEL


debug DEC 09,DAT1,DAT2,DAT3,13,10 'Message confirming reception


for ct=0 to 10
toggle INTLED
toggle MESLED
pause 500
next ct




'RETURN TO PROGRAM
IOCAF=%0
@ INT_ENABLE IOC_INT
@ INT_RETURN
;-------------------------------------------------------------------------------
Thanks for the help