Re: [f-cpu] manual 0.2.5 quirks

[Yann Guidon <whygee@f-cpu.org>]

hi !

Michael Riepe wrote:

> I'm currently busy with something different (in case you're nosy:
> symbolic verification of the F-CPU execution units) but I stopped to
> have a look at the PDF version of the latest manual...
> 
> .... and I still found some quirks in the instruction set part:
> 
> - Register naming is inconsistent in sub and div:
> 
> 	sub r3, r2, r1 => r1 = r2 - r3
> 	div r3, r2, r1 => r1 = r3 / r2
> 
>   The `sub' variant is more logical.
For the division, the divisor should be R3
so we can easily catch division by zero.

> - The current ASU sets the `borrow' register to 1, not -1.
>   See vhdl/eu_asu/iadd.vhdl, line 344ff.
do you number lines in hexa ?

> - The description of `subi' is wrong (registers swapped):
> 
> 	subi imm8, r2, r1 => r2 = r1 - imm8
> 
>   In general, <op>i and <op> should be consistent. That is, the
>   instruction is supposed to calculate `r1 = r2 - imm8'.
sure.

> - The `alternate result register' is still named `r1+1' throughout the
>   manual. Didn't we change that to `r1^1'?
right too.

<snip>

i'll try to assist Cedric when he updates it.

WHYGEE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*************************************************************
To unsubscribe, send an e-mail to majordomo@seul.org with
unsubscribe f-cpu       in the body. http://f-cpu.seul.org/