[SOLVED] PIC code improvement

[dmta]

Dear all,

I have this program where inside a timer interrupt I need to carry out certain things. One of this is to execute the following line of code. But when I do this the microcontroller takes some time to compute the value. Can you give me any suggestions to improve it? the variables are in type int

 z_n = xor + ((z_n*63)>>6);
          xor_sum = z_n>>6;

Best regards

 

[horace1]

cannot see any obvious way to improve performance - clearly the * is the longest operation - can you give more details of the algorithm?
how often does the timer interrupt? if only mSeconds there should be no problem but get 50000 interrupts/second and you could have timing problems
can you increase the processor clock by using clock multipliers which are available on the more powerful PICs?

 

[Simao.Berkof]

Dear all,

I have this program where inside a timer interrupt I need to carry out certain things. One of this is to execute the following line of code. But when I do this the microcontroller takes some time to compute the value. Can you give me any suggestions to improve it? the variables are in type int

 z_n = xor + ((z_n*63)>>6);
          xor_sum = z_n>>6;

Best regards

I would try to convert

z_n*63 -> ((z_n << 6) - z_n) // = z_n * 64 - z_n = z_n*(64-1)




Re writing

 z_n = xor + (((z_n << 6) - z_n)>>6);
          xor_sum = z_n>>6;

Hope it helps.

Simao

 

[horace1]

 z_n = xor + (((z_n << 6) - z_n)>>6);
          xor_sum = z_n>>6;

looks an interesting solution!

 

[dmta]

very sorry for this late reply... the answer is correct. !!!!!!!!!!!!!!!