USART interrupt not interrupting right

[Morpheus]

Now I'm not interested on data packets. I'm just trying to address one slave, so the only thing that I'm doing is to send JUST ONE BYTE on the serial port.
This byte is the address byte. If the slave is addressed, he has to do something(to turn on a led?), otherwise he will resume.
I tried to do this, but he worked only in the 40% of the sent bytes.

So I wrote that code to save in the eeprom what char the pic was receiving. And I saw that the char was right only 40% of times.

For example:
-1st try
PC: %1 0000 0001
PIC: interrupt, read RCREG, received char:%0000 0001 (this is right)

-2nd try
PC: %1 0000 0001
PIC: interrupt, read RCREG, received char:%0110 0111 (????????? whi????)

-3rd try:
PC: %1 0000 0001
PIC: interrupt, read RCREG, received char:%0000 0001 (this is right)

-4th
PC: %1 0000 0001
PIC: interrupt, read RCREG, received char:%0100 1001 (????????? whi????)

-5th
PC: %1 0000 0001
PIC: interrupt, read RCREG, received char:%0011 0101 (????????? whi????)

-6th
PC: %1 0000 0001
PIC: interrupt, read RCREG, received char:%0111 0111 (????????? whi????)


....
and so on...
The idea of sending the data byte with only 8 bits is ok, but, for the moment I'm just testing the address detection..
But if I send 1 byte, and when I read it this is not the byte I sent, even if the ninth bit has generated the interrupt, the slave will not work because it thinks it's not addressed!!

The problem is that I'm expecting a byte in the RCREG and what I find is another one (random?). I don't know if this depends on the registers or what, but testing with an oscilloscope on the USART rx pin, the byte is right, and is just ONE! It's so strange he gives me a completely different value!

Is possible that when the pic saves the registers going in interrupt, he changes the value of the RCREG?

[Bruce]

Please post the code you're working with, and I'll have a look

[Morpheus]

Thank you for your patience..

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)

'set the speet to 38800 baud (with a 10Mhz osc)
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


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
ADEN VAR RCSTA.3



Enable interrupt


i VAR WORD
led VAR BIT
led2 VAR BIT
ric VAR BYTE
ric2 VAR BYTE
X VAR BYTE
X=0


on interrupt GoTo indirizzo

GoTo ricevi


 Disable
indirizzo:

    ric = RCREG            'store the byte contained on RCREG in "ric" and clear RCREG

    
    While RCIF               'to be sure that the register'll be empty the next time I'll read it
       	ric2=RCREG
    Wend
    
'    ADEN=0
'    RCIF=0   
    
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 3 lsb of ric into 3 external leds
     PORTA.0=ric.2
     PORTB.7=ric.1
     PORTB.6=ric.0   
     
             'every time that the pic is interrupted, store the received byte in a location into the eeprom
	Write 0+X,ric
	X=X+1          'next time will write the next location

  Resume
 Enable


ricevi:

	For i=1 to 65000
	Next	

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

[Bruce]

Try this. It's tested on a 16F627a @4MHz using the MicroCode Studio terminal program.

I suspect your problem may be due to data-rate errors & trying to write to EEPROM with interrupts enabled. This works perfectly at a data-rate of 19,200 @ 4MHz.

Use a PC RS232 terminal program that will allow you to send/receive with odd or even parity & view the results on your terminal program. The PIC is setup to send & receive 9-bit.

This will echo the received address byte back to the PC terminal software using 9-bit send & receive 9-bit with auto address detect. An LED on RB0 will toggle only when in the interrupt service routine.

Note: If you have your PC terminal software set for EVEN parity, then the program (PIC) will only respond to 1,2,4,7 or 8 because these values will generate a logic 1 as the parity bit which the PIC *must* see in 9-bit mode.

If you set it for ODD parity, the PIC will only respond to 3,5,6,9 or 0.

Any value sent to the PIC that does not generate a logic 1 as the 9th parity bit will be ignored, and no interrupt will be generated.

DEFINE OSC 4

OERR    VAR RCSTA.1    ' (Read Only) USART over-run bit
CREN    VAR RCSTA.4    ' Alias USART continuous receive enable bit
RCIF    VAR PIR1.5	  ' (Read Only) USART received character interrupt flag bit
ADEN    VAR RCSTA.3    ' Alias Address enable bit (for 9-bit mode)
X       VAR BYTE       ' GP
PORTB.0 = 0            ' Initialize port bit
TRISB.0 = 0            ' RB0 = LED interrupt indicator

'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=1 '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=1 '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

SPBRG = 12 ' 19,200 bps @ 4MHz 16F627a

ON INTERRUPT GOTO IntHandler

Main:
   FOR X = 0 TO 255    ; Waste some time waiting for characters
    PAUSEUS 10
   NEXT
   GOTO Main

    DISABLE
IntHandler:
    PORTB.0 = PORTB.0^1 ' Indicate that we are in interrupt routine
    IF RCIF THEN        ; Read characters from RCREG only when RCIF is set
      @ movf RCREG, W   ; Load RCREG into W
      @ movwf TXREG     ; Transmit back to PC
    ENDIF
    ' Clear over-runs if present
     IF OERR = 1 Then   ' If over-run, then clear it
        CREN = 0        ' Disable receive
        CREN = 1        ' Re-enable & clear over-run condition
     EndIF
    Resume
    Enable
    END

[Morpheus]

It's not possible!
You can't believe where was the problem!
It was a hardware problem!!:
I'm using a rs485 net, and there was a short-circuit on the Tx-enable pin of my rs485 converter..
so the char I was reading was noised by strange trasmissions on the line!!! the char I were sending was right, but the received one was mixed with other stranges things..

sorry. The program was working right.
Thank you Bruce for your attention.
C yA
Simone.