How to write data into a sfr register????

[anupama619]

Hai
How can I able to write a data into sfr registers??? I am using PIC16f877a and I want to write into INTCON register. But when I am using INTCON it showing error. Can anybody help me??? I am giving my code..
code:
SET_TRIS_B(0x01);
INTCON=0x00;


Hoping areplay

Thanks in advance.......

[Ttelmah]

Just declare INTCON....

By default, CCS, does not 'know' the function register names, since in general it is not necessary to use them. So the normal way to write to INTCON, in CCS, is to use the disable/enable interrupts function. However if you want to do something like clear all the bits at once, as you show, then just declare the register. So:

[anupama619]

Thanks for your reply. Now it is working.

[rnielsen]

If you want to have direct access to the sfr registers you, first, need to tell the compiler the address of each register you want to access. Then, you can define each bit in the register if you want.

[anupama619]

Sir,
In my project I want to receive more than 3 external interrupt. But now I am working with PIC16f877A. So I wrote a code like this.
CODE:

#include <16F877a.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

#INT_EXT
void ext_isr()
{


if(input(PIN_B5))
{
printf("First Interrupt\n\n");
}
if(input(PIN_B6))
{
printf("Second Interrupt\n\n");
}
if(input(PIN_B7))
{
printf("Third Interrupt\n\n");
}

}
// main program that increments counter every second
void main()
{
long counter;

ext_int_edge(H_TO_L); // init interrupt triggering
enable_interrupts(INT_EXT);// turn on interrupts
enable_interrupts(GLOBAL);

printf("\n\n");
counter=0; // reset the counter
while(TRUE)
{
printf("The count value is: %5ld \r\n",counter);
counter++; // display count value and increment
delay_ms(1000); // every second
}
}
Pins B5, B6, & B7 are connected to positive point of 3 diode, which are the 3 interrupt points also. In my Isr routine I am checking for the interrupt. But it is not giving a proper output. Can anybody help me?.. Hoping a replay. Thanks in advance..

[Ttelmah]

You are using the wrong interrupt.

INT_EXT, is an interrupt on the external interrupt pin - B0, on an 877. To detect changes on the four high port B pins, you need to use the PortB changed interrupt (INT_RB).

Remember also that the interrupt on these pins, will trigger when the pins fall, as well as when they rise (there is no programmable 'edge' detection on this interrupt), and pin B4, will also trigger the interrupt.

Best Wishes

[anupama619]

Thanks for your reply.

But when I am using #INT_RB it is not entering in to the ISR routine. Here I am giving my code.

[Ttelmah]

First thing, you _must_ read port B, inside the RB interrupt. Otherwise if the interrupt does trigger, it'll trigger for ever.....
Then, the key 'reason' you are not getting to the ISR, is you are not enabling the interrupts anywhere. You need to enable INT_RB, and the GLOBAL interrupt flag, before the interrupt routine will be called...

Best Wishes

[anupama619]

Thanks for your reply.

I changed my code like this:

[bkamen]

[RckRllRfg]

A quick thanks for this post. These are the gems that make the forums so useful.



RckRllRfg