Multiplication on MPLAB - PIC16F84A

[dannyelloko20]

I need some help on how to multiply a hex value five times using asm code. Im stuck and cant start my project.

Thanks in advance.

 

[d3javu]

Hi danny, hope the link below gives you rough idea on how to play with multiplication.
http://picprojects.org.uk/projects/pictips.htm#8_x_8_multiply

 

[dannyelloko20]

Good stuff! However im dealing with a PIC16F84A and the instructions on the link above are different. Thanks though i can actually use the examples they have to get a better idea as to how the logic works.

 

[betwixt]

??? those ARE instructions the 16F84A understands. MPLAB creates aliases for the 'skp' instructions, they are mentioned in the MPLAB help files and earlier in the web link.

Trick: if you know the RESULT is going to fit in 8 bits (no greater than 255), you can do it in fewer instructions:

1. enter with the value in W.
2. copy W to a memory location.
3. shift it to the left (now holds 2 * value)
4. shift it to the left (now holds 4 * value)
5. add W to the memory location.

Depending on whether you set W or the memory as the destination, it now holds (value + (value * 4)) = value * 5.

Brian.