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gokulrred
Joined: 22 Nov 2011
Posts: 32
Location: puducherry
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| handling two interrupts.... how???? |
 Posted: Wed Jan 11, 2012 6:09 am |
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i want to use SSP interrupt for spi....
and while SSP ISR completes my program will make hardware to generate interrupt.
that interrupt i am using in CCP1...
is it possible? |
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asmallri
Joined: 12 Aug 2004
Posts: 1635
Location: Perth, Australia
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| Re: handling two interrupts.... how???? |
| Posted: Wed Jan 11, 2012 7:48 am |
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| gokulrred wrote: | i want to use SSP interrupt for spi....
and while SSP ISR completes my program will make hardware to generate interrupt.
that interrupt i am using in CCP1...
is it possible? |
Some PICs support multiple interrupt vectors. The PIC18F supports high and low, the PIC24 and dsPIC support multiple. The PIC16F supports only a single interrupt vector.
PICs with multiple vectors support multiple priority levels. The PIC18F (the most basic PIC supporting multiple vectors) has a high priority vector and a low priority vector. The PIC24 and dsPICs have multiple levels of priority.
For PICs with multiple interrupt vectors, a higher priority interrupt will interrupt a lower priority interrupt handler.
CAUTION: The CCS compiler has a different concept of interrupt priorities which predated PICS with unique vectors per source. This priority is used to determine the interrupt handler processes interrupts of the SAME hardware priority HOWEVER by default when an interrupt occurs interrupts of the same or lower hardware priority are disabled. Unless you really know what you are doing, you should not enable interrupts of the same priority inside the interrupt handler.
Back to your specific case, There is NO reason that processing SSP interrupts should take more than a few clock cycles. If it does then you have a logic error in your coding. For example, in an interrupt handler if you are writing out a data value you should never wait inside the handler for the byte to have been sent.
_________________
Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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gokulrred
Joined: 22 Nov 2011
Posts: 32
Location: puducherry
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| Posted: Wed Jan 11, 2012 10:12 pm |
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Thank you for your valuable comments...
I am using PIC 18F4431.
| Code: |
#int_SSP
SSP_isr()
{
val1 = spi_read();
if(val1==0x80)
{
output_bit(PIN_C6,1);
output_bit(PIN_C7,0);
delay_ms(10);
output_bit(PIN_C6,0);
}
}
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The above code I've written in SSP ISR,
so when slave PIC gets SPI data it'll get interrupted.
Upon which it makes C6 =1 and C7=0.
In those ports I connect motor.
When the motor rotates its encoder generate pulse.
That pulse I want to take in CCP1.
1. My doubt is how to implement this ?
2. As soon as motor gets power for 10ms, it gets rotated and encoder generates pulse. Will it give an interrupt before the last line "output_bit(PIN_C6,0);" gets over ?
How to handle the interrupts ?
I want SSP to have high priority and CCP1 low priority. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19553
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| Posted: Thu Jan 12, 2012 2:31 am |
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Which is why you should never delay in interrupts....
The simple rule is that an interrupt should do what is necessary to handle the hardware event it signals, and nothing else.
You should just read the spi in the SPI interrupt. Then if the value is the one you need to set the bits, set these, and either set a flag, then clear the bit in your main a few mSec latter, or start a hardware timer, to trigger 10mSec latter, and when this interrupts, then use it to clear the output bit.
Delays in an interrupt of more than a very few uSec, kill the whole point of using interrupts.
Best Wishes |
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gokulrred
Joined: 22 Nov 2011
Posts: 32
Location: puducherry
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| Posted: Fri Jan 13, 2012 6:41 pm |
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@Ttelmah:
ya sir...
using delay will be not a good idea...
but i want to make D6 =0 and D7=1 when i get 0x80 data throu SPI.
and D6=1 and D7=0 when i get 0x81 data throu SPI in the slave side.
in both cases i want to make those terminals in that state and make them zero in 10 ms.
is there any other way to implement this? |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19553
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| Posted: Sat Jan 14, 2012 2:58 am |
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Yes I've already told you how to do it.....
Just use another timer ISR to clear the bits 10msec later.
Best Wishes |
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