Assembly programming problem with CNT
HGPL
Posts: 15
Hi,
I worry about the code below:
The waitcol is working. The waitcol2 not working...
I think make the fixrate wait with a pin verifying capability, and the waitcnt not good here...
Anybody know help for me...?
thanks, Gabor
Post Edited (HGPL) : 11/6/2007 4:18:41 PM GMT
I worry about the code below:
mov wcol,#1
shl wcol,#28
...
call #waitcol or call #waitcol2
...
waitcol2
mov tnextcol,cnt
add tnextcol,wcol
cmp cnt,tnextcol wc 'c=1; cnt < tnextcol
if_c jmp waitcol2
waitcol2_RET ret
waitcol
mov clk,cnt
add clk,wcol
waitcnt clk,wcol
waitcol_ret ret
The waitcol is working. The waitcol2 not working...
I think make the fixrate wait with a pin verifying capability, and the waitcnt not good here...
Anybody know help for me...?
thanks, Gabor
Post Edited (HGPL) : 11/6/2007 4:18:41 PM GMT
Comments
waitcol2 mov tnextcol, cnt add tnextcol, wcol cmp cnt, tnextcol wc 'c=1; cnt < tnextcol if_c jmp waitcol2 waitcol2_RET ret(1) JMP #waitcol2B
(2) Set the label waitcol2B before the CMP; you have I fine moving target with your original code
Very thanks... [noparse]:)[/noparse] last hour was very poor for me...
HVALA
The # is a very high blame... [noparse]:)[/noparse]
but... [noparse]:)[/noparse]
'first column delay init mov wcol,#1 shl wcol,#19 mov tnextcol,cnt add tnextcol,wcol ... call #waitcol2 ... waitcol2 cmp cnt,tnextcol wc 'c=1; cnt < nextcnt if_c jmp #waitcol2 mov tnextcol,cnt add tnextcol,wcol waitcol2_RET ret... and not working yet...
Post Edited (HGPL) : 11/6/2007 4:37:53 PM GMT
It is working, but I don't know why need the T1 temporarily variable...
Is CNT not working with CMP command?
waitcol2 mov t1,cnt cmp t1,tnextcol wc 'c=1; cnt < nextcnt if_c jmp #waitcol2 mov tnextcol,t1 add tnextcol,wcol waitcol2_RET retThe rule is: Never use a "special register" at the DEST operand unless you exactly know what you are doing..
The reason: You will not read:
- CNT
- INA
- PAR
- PHSA
- PHSB
as expected!
Rather you will read what you last have written to it. This is well know as "The Behaviour Of The Shadow Registers"
You can fix it in your second example by just reversing CNT and TNEXTCOL and jumping IF_NC
Another note: Once every 40 to 50 seconds your program will fail, when the CNT overflows from $FFFF_FFFF to $0
I will read deep the documentation [noparse]:)[/noparse] thanks.
My setup is _CLKMODE = RCFAST
The fail wait about 6 minutes and i will correct the code but this mistake not matter for my app.
thanks
You can avoid using the temp variable 't1' if you use cmpsub instead of cmp
waitcol2 cmpsub tnextcol, cnt wc, [color=#0]nr[/color] 'c=1 if tnextcnt is greater than or equal to cnt if_c jmp #waitcol2 mov tnextcol, cnt add tnextcol, wcol waitcol2_RET ret▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/7/2007 7:55:08 PM GMT
but this last code is not working...
I read the CMPSUB doc, and I think the code is ok, but the CNT usage is not working with this command...
Post Edited (HGPL) : 11/6/2007 6:06:27 PM GMT
(1) You have to read the "Erratum" www.parallax.com/dl/docs/prod/prop/PMv1.0Supplement-v1.3.pdf
The description of the CMPSUB instruction is not only absolutely confusing in the Manual, it is WRONG!
(2) You don't need CMPSUB! Your program will work fine, when you just reverse the operands of CMP and JUMP if NC, as I described above...
BTW: The Eratum 1.3 now contains detailed hints wrt the "Shadow Registers"
Edited...
Post Edited (deSilva) : 11/6/2007 11:09:41 PM GMT