USART interrupt not interrupting right

[Morpheus]

Hi All!

I'm working with a 16f628A

I wrote a "simple" code, the interrupt has just to turn on a led when a 9-bit char with the 9th bit enabled is received on the usart rx port.

the main program just make blinking a led.
the results are that if I receive an address(8 bit char with the 9th bit set), the blinking led remains on(or off) doubling the time(2 secs instead 1), and the led that the interrupt had to turn on, remains off.

I'll post my code.

CODE:
----------------------------------------------------------------------
INCLUDE "MODEDEFS.BAS"

TRISA=%11110000
TRISB=%00000010

cmcon=7 ' predispone la portaA come I/O digitali


'INTCON ( Interruption Control register )
intcon.7=1 'GIE : Global Interrupt Enable bit
intcon.6=1 'PEIE : Peripheral Interrupt Enable bit ( This bit should be set when using the CCP interruption so on )
intcon.5=0 'T0IE : TMR0 Overflow Interrupt Enable bit
intcon.4=0 'INTE : RB0/INT Interrupt Enable bit
intcon.3=0 'RBIE : RB Port Change Interrupt Enable bit
intcon.2=0 'T0IF : TMR0 Overflow Interrupt Flag bit
intcon.1=0 'INTF : RB0/INT Interrupt Flag bit
intcon.0=0 'RBIF : RB Port Change Interrupt Flag bit

'definisco il registro di ricezione RCSTA
rcsta.7=1 'SPEN serial port enable bit
rcsta.6=1 'RX9 9-bit receive enable bit
rcsta.5=0 'SREN single receive enable bit
rcsta.4=1 'CREN continous receive enable bit
rcsta.3=1 'ADDEN address detect enable bit
rcsta.2=0 'FERR framing error bit(read only)
rcsta.1=0 'OERR overrun error bit(read only)
rcsta.0=0 'RX9D 9th bit of receive data (read only)


'definisco il registro di trasmissione TXSTA
txsta.7=0 'CSRC : Clock Source Select bit
txsta.6=0 'TX9 : 9-bit Transmit Enable bit
txsta.5=1 'TXEN : Transmit Enable bit
txsta.4=0 'SYNC : USART Mode Select bit 0=asincrono
txsta.3=0 ' N/A
txsta.2=1 'BRGH : High Baud Rate Select bit
txsta.1=0 'TRMT : Transmit Shift Register Status bit ( Read only )
txsta.0=0 'TX9D : 9th bit of transmit data. Can be parity bit.


'PIE1 ( Peripheral Interrupt Enable register ) 8Ch
PIE1.7=0 'EEIE : EE Write Complete Interrupt Enable Bit
PIE1.6=0 'CMIE : Comparator Interrupt Enable bit
PIE1.5=1 'RCIE : USART Receive Interrupt Enable bit
PIE1.4=0 'TXIE : USART Transmit Interrupt Enable bit
PIE1.3=0 ' N/A
PIE1.2=0 'CCP1IE : CCP1 Interrupt Enable bit
PIE1.1=0 'TMR2IE : TMR2 to PR2 Match Interrupt Enable bit
PIE1.0=0 'TMR1IE : TMR1 Overflow Interrupt Enable bit


'azzera tutti i flag di interrupt
PIR1.7=0
PIR1.6=0
PIR1.5=0 'azzera l'RCIF
PIR1.4=0
PIR1.3=0
PIR1.2=0
PIR1.1=0
PIR1.0=0



'DEFINE HSER_BAUD 38400 ' Set baud rate
'DEFINE HSER_SPBRG 15 ' Set SPBRG directly (normally set by HSER_BAUD)

'setta la velocità a 38800
SPBRG.7=0
SPBRG.6=0
SPBRG.5=0
SPBRG.4=0
SPBRG.3=1
SPBRG.2=1
SPBRG.1=1
SPBRG.0=1



DEFINE OSC 10




Enable interrupt


i VAR WORD
led VAR BIT
led2 VAR BIT
ric VAR BYTE



on interrupt GoTo indirizzo

GoTo ricevi


indirizzo:

' HSerin [ric]'riceve un carattere da seriale
' IF led2=1 Then
' PORTA.0=0:led2=0
' Else
' PORTA.0=1:led2=1
' EndIF
PORTB.7=1

Resume


ricevi:

For i=1 to 65000
Next

IF led=1 Then
PORTB.6=0:led=0
Else
PORTB.6=1:led=1
EndIF
GoTo ricevi

-------------------------------------------------------------------
/CODE


I hope someone can help me..
Thanks,
Simone
P.S. Sorry for my english!

[Bruce]

You always want to clear interrupt flag bits before re-enabling interrupts.
RCIF is the serial receive interrupt flag.

Since RCIF is read-only, you need to read RCREG until it's empty to clear
RCIF. You'll also want to clear any over-run conditions.

OERR VAR RCSTA.1    ' Alias USART over-run bit
CREN VAR RCSTA.4    ' Alias USART continuous receive enable bit
RCIF VAR PIR1.5	    ' Alias USART received character interrupt flag bit

Try adding this to your BASIC interrupt routine.

     DISABLE
indirizzo:
     PORTB.7 = PORTB.7 ^ 1   ' Toggle LED on entry to int handler
     IF OERR = 1 THEN   ' If over-run, then clear it
        CREN = 0   ' Disable receive
        CREN = 1   ' Re-enable & clear over-run condition
     ENDIF
     WHILE RCIF   ' If RCIF is set, then read RCREG until it's clear
        X = RCREG
     WEND
     RESUME
     ENABLE

[Morpheus]

Thank you Bruce for the answer, now the pic is interrupting, but I have a problem reading the register right..

indirizzo:

    ric = RCREG

    
    While RCIF                   'to be sure that the register'll be empty the next time I am going to read it
       	ric2=RCREG
    Wend
    
     IF OERR = 1 Then   ' If over-run, then clear it
        CREN = 0   ' Disable receive
        CREN = 1   ' Re-enable & clear over-run condition
     EndIF
     

     'print the first 3 bit of the received char on three external leds
     PORTA.0=ric.2
     PORTB.7=ric.1
     PORTB.6=ric.0
     
     
	Write 0+X,ric           'write the received byte in the eeprom
	X=X+1  

	
	
  Resume
 Enable

I am just sending to the pic a 9-bit char like this: 1 0000 0001
the 9th bit generate the interrupt, and "ric" has to be 1.
so at the end I have to read X locations of my eeprom programmed with a "01h" byte.

in the fact I have only the 40-50% of the x locations with 01, and the others has a random-like value (FF, E9, 9b, FE......).

naturally the problem is not on writing the eeprom, because the 3 external led shows that the byte is far from "01h"!!!

I can't explain why this happens, do you?

Thanks a lot
Simone.

[Bruce]

If you need the 9th bit, then simply read it from RCSTA.0 (as shown in your datasheet) before reading RCREG.

Example;

Received 9-bit data = %1 1010 0011

ric var word

ric.HighByte = RCSTA & %00000001 ' Read RCSTA bit #0 into ric bit #8
ric.LowByte = RCREG

ric now contains %0000 0001 1010 0011

[Morpheus]

sorry, I think I didn't explain myself well..

I don't need the 9th bit, it works well 'cause I need it just to interrupt the pic.
I need to read the correct address, but I don't know why the char is not always correct.

for example in 10 sended char, 10 times that the pic generates the interrupt and 10 times that i've the rcreg in the var ric. But "ric" contains only 4-5 times the char that I've sent (00000001), the other times it contains random values. The char that I've received is non the one I've sent!!!
I tryed with the "Hserin [ric]" command instead ric=RCREC, but it's the same.

I used the Usart port well without interrupt before, with the same speed (38400) and the received char was ALWAYS correct. I can't explain myself why now I've this problem!!
I took all the last night trying to solve this problem, without success.

[Bruce]

Are your data packets coming in *all together* or is there a delay between each 9-bit packet?

Are you 100% sure the transmitting device is sending 9-bit packets?

[Morpheus]

The device (pc) is sending 9-bit packet,
I am sure that it works because if I send a packet with the 9th bit =1, it interrupts, if the 9th bit is=0 it don't.

the device is sending just 1 byte for time. I just made a program that has a button. every click on this button sends a 9-bit packet to the serial port.
I can choose the byte sent, and I can choose if the 9th bit is set or nope.
I also tested it with an oscilloscope. And the 9 bits are correct.