PIC generate random number using feedback shift register

[the_merovingian]

I'm interesting in generating some random numbers for one of my projects.

I have stumbled across the following code snippet:

https://www.phanderson.com/PIC/16C84/random.html

It appears to use feedback shift registers to generate a pseudo random sequence.

Does anyone have any thoughts / comments / better examples?

Many thanks in advance.

 

[betwixt]

I seem to remember a simpler program was discussed on the Microchip Forum a few months ago. It might be worth searching there for it.

Try: https://www.microchip.com/forums/tt.aspx?forumid=-2

Brian.

 

[the_merovingian]

Thanks, I assume you're talking about:

https://www.microchip.com/forums/tm.aspx?m=445200&mpage=1&key=&#445200

In which they reference AN544 (Math Utility Routines):

https://ww1.microchip.com/downloads/en/AppNotes/00544d.pdf

0311      Random16
0311 1A19          rlcf   RandHi,W
0312 0C19          xorwf  RandHi,W
0313 1B0A          rlcf   WREG, F   ; carry bit = xorwf(Q15,14)
          ;
0314 1D19          swapf  RandHi, F
0315 1C18          swapf  RandLo,W
0316 230A          rlncf  WREG, F
0317 0C19          xorwf  RandHi,W  ; LSB = xorwf(Q12,Q3)
0318 1D19          swapf  RandHi, F
0319 B501          andlw  0x01
031A 1B18          rlcf   RandLo, F
031B 0D18          xorwf  RandLo, F
031C 1B19          rlcf   RandHi, F
031D 0002          return

I only needed 8bit number (above generates 16bits) but that's a good starting point thanks.