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[f-cpu] Comment on Manual 0.2.6



Hello,

At last, I have entirelly read the manual, and I have
some error or problems.

On the content, I have see one big error on the
instruction set and some minor mistake :

* The big error is on the function description of
"expand" instruction (p.140), it is give :

" This is the reverse operation of the "mix"
instruction..."

This is false, if we look the figure 2.2, take the
following example :

r1="12345678" r2="abcdefgh"

mixl r1,r2,r3 => r3="1a2b3c4d"
mixh r1,r2,r4 => r4="5e6f7g8h"

expandl r3,r4,r1 => r1="15263748"
expandh r3,r4,r2 => r2="aebfcgdh"


If expand is the reverse operation of mix then r1
before and after mix and expand sequence must be
equals.

* Some minor errors are into example of "sub" and
"addsub" instructions (p.80 and 93).

I am not a genius;-), but if r1=r2-r3 and r3 <= r2
then r1 >= 0 :-P.

With : r1=0x05 and r2=0x07
We have : sub.b r1,r2,r3 => r3=0x02 in any case

and if (r1)+1=r2-r3 and r3 <= r2 then (r1)+1 >= 0 :-P.

with : r1=0x23 and r2=0x36
We have : addsub.b r1,r2,r3 => r3=0x59 and r4=0x13

* In chapter 3.3 (p.54) in paragraph 4, the text
"...number is cleared : 0>1, 11>10..."  must be
replaced by "...number is cleared : 1>0, 11>10..." 

On the presentation aspect, I have many remarks :

* It is better if chapter (and Part title) begin on
the right page (I have made a recto-verso printing and
lot of chapter began on left page).
* In part IV - advanced topics, the text before the
chapter 1 (p.59) can be included into a chapter named
Overview.
* It seems missing a mandatory package into the tex
header, because all the mathematic symbols like sqrt
is transforme, likewise with "r1+1" (to say the r1's
follower register) wich become : r1&1circ;
* It is better if we begin the Instruction Set section
by a "notation" section where we gave the syntax
legend, like "When an instruction is given into the
description of function object, it is write into
italic bold" in example.
In that case, we can remove the " into description of
addi (p.95) into "...to the add" instruction..." ;-)
* In Performance section of each instruction, the
"Execution Unit" name could be followed by its short
abbrev.
* Into chapter VI.2, the "Flag" definition tables
overflow on the right side (and I miss the end of the
definition)
* For "bitop" and "bitopi", the F tables aren't
similar of presentation used with other instruction,
more the "bitopi" and the "bitop" format presentation
are different one give F only inside the "Flag"
definition, the other give it into the flag and
outside.
* The following instructions haven't the same bits
ordering, inconsistent with the the format description
gived into chapter V.2, than others: "logic",
"logici", "move", "loadaddr".
* In chapter VI.4 on floating point operations, a
default operator size must be given.
* In chapter VI.5, to describe the endian flag, the
presentation must be uniformized on the model of other
parameter (1 if big endian => loade by example).
* In paragraph VI.5.2.5, it missing the format
description and the flag explanation.
* In paragraph VI.5.2.6, the memory level postfix must
be lowercase.
* In "move" and "jump" instructions, the conditions
postfix "-nz, -nm, -nl" are redundant with the Flag 10
definition. More the Condition definition table and
the Flag definition tables must be coherent => merge
bit 10 to 12 under name Condition oder split them like
negation/condition and adapt the second table.



Some spelling mistakes:
* In chapter III.3.4 (p.55): "...For these reason, it
would is difficult..." must be replaced by "...For
these reason, it would be difficult..."
* In chapter IV.1 into the third cause (p.61):
"...otherwise the result will sturate..." must be
replaced by "...otherwise the result will saturate..."
* In chapter V.1 (p.69) in second paragraph: "For the
F-CPUU..." must be replaced by "For the F-CPU..." and
"...(ISA) faces a lot of constraints and
evolitivity..." must be replaced by "...(ISA) faces a
lot of constraints and evolutivity..."
* Into the Instruction set draft section, you have
many "...wrap"..."

Other topics:
* In chapter IV.3-Scheduler (p.66), what meens: "On
average, it is propable that the 2 write ports of the
register set are used 70the data is actually
available"
I don't understand "70the" :-?
* In chapter V.1 (p.69), the figure 1.1 and the text
are inconsistent with the instructions format
description gived into chapter V.2 (p.71) (same
remarks on chapter V.2 text).
Into the description, the opcode is localized into bit
31 to bit 24 position, which is a MSB position, and
the destination register is given on LSB position.
* In case of "popcounti" : If the Imm8 parameter is
really optional, we can add a remark to signalized
than "popcount" is functionnaly equivalent to
"popcounti" without r3 and Imm8





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