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I2C slave in EX_SLAVE.C

 
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PICoHolic



Joined: 04 Jan 2005
Posts: 224

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I2C slave in EX_SLAVE.C
PostPosted: Wed Nov 01, 2006 4:33 am     Reply with quote
Hello
Given the following code [16F88] (extracted from EX_SLAVE.C):
Code:

#INT_SSP
void ssp_interupt ()
{
   BYTE incoming, state;

   state = i2c_isr_state();

   if(state < 0x80)                     //Master is sending data
   {
      incoming = i2c_read();
      if(state == 1)                     //First received byte is address
         address = incoming;
      if(state == 2)                     //Second received byte is data
         buffer[address] = incoming;
   }
   if(state == 0x80)                     //Master is requesting data
   {
      i2c_write(buffer[address]);
   }
}

I tried to simulate it on PROTEUS - ISIS.
I had to replace
Code:
if(state == 1)
to
Code:
if(state == 0)

and
Code:
if(state == 2)
to
Code:
if(state == 1)
to make it work.
Where's the bug? CCS or PROTEUS?
(I didnt try it physically)

Thanks
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Nov 02, 2006 1:07 am     Reply with quote
The i2c_isr_state() function looks at the DA and RW bits in the SSP
control registers. If Proteus emulates those bits incorrectly, then
you will have a problem.

If you want to research it further, here is some more information
on the i2c_isr_state() function:

This post shows the ASM listing of the i2c_isr_state() function:
http://www.ccsinfo.com/forum/viewtopic.php?t=28531&start=10

This post shows C code which does the same thing as i2c_isr_state():
http://www.ccsinfo.com/forum/viewtopic.php?t=26477&start=3
PICoHolic



Joined: 04 Jan 2005
Posts: 224

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PostPosted: Thu Nov 02, 2006 1:17 am     Reply with quote
Thank you
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