From Newsgroup: comp.sys.cbm

Hi there...

I don't know if this is the right Group, but since there ist no comp.lang.6502... :)
I just startet again to program my c64 in Assembler (I'm quite astonished
that I still know that much) and now I realize that I can't remember some
very simple things:

- How can I display the Value of an Adress on the Screen in _decimal_? IIRC there is some routine in the BASIC-Rom which can do this, but I'm not sure. and reading through the Memory-Map-Document from project 64 didn't help
either

- What is the fastest way to put text on the screen? I think it's by
POKEing the Values right into the Scrren RAM ($0400) but I still know there are Kernel-Routines called "CHROUT" or "STROUT" or something like that.

- How can I turn on and off the LED of the Floppy? I have seen some Demos which do this, should be just one POKE ?

And generally I'm looking for some complete Documentation to the Opcodes of the 6502, even the "illegal" ones.

Thank's a lot for your help!

David
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From Newsgroup: comp.sys.cbm

And generally I'm looking for some complete Documentation to the Opcodes of the 6502, even the "illegal" ones.

http://www.the-dreams.de/aay.html

Hope it helps :)

Best wishes

Ninja / The Dreams

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From Newsgroup: comp.sys.cbm

Hmm, I'd try

; Turn LED on
LDA #$08
ORA $1C00
STA $1C00

and

; Turn LED off
LDA $1C00
AND #$F7
STA $1C00

executed inside the 1541. There is no single routine for turning it off,
only inside the power-up self-test. For turning the LED on, you could also
try to do a "M-E" command with address $C118. But I think you have to upload these commands by yourself before you can turn the LED on and off... You definitely can't do this with POKEing in the C64 RAM.

Thomas


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From Newsgroup: comp.sys.cbm

http://project64.c64.org/hw/c64.html

more resources at
http://www.funet.fi/pub/cbm/index.html
ftp://ftp.funet.fi/pub/cbm/index.html
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From Newsgroup: comp.sys.cbm

On 14 Jul 2003 08:36:33 GMT, David Mueller
<david.mueller@post.rwth-aachen.de> wrote:

- How can I display the Value of an Adress on the Screen in _decimal_? IIRC >there is some routine in the BASIC-Rom which can do this, but I'm not sure.

You can, of course, just do the arithemetic, by dividing repeatedly by
10 .. each time, the remainder is a decimal digit which you can
convert to ASC/PTSC printable with a simple OR command. (Division is
a whole other subject). Another way to do the arithmetic elegantly is
an algorithm to use decimal mode to quickly convert binary to decimal
(again, details not included; if interested, ask).

- What is the fastest way to put text on the screen? I think it's by
POKEing the Values right into the Scrren RAM ($0400) but I still know there >are Kernel-Routines called "CHROUT" or "STROUT" or something like that.

POKE-ing is faster than CHROUT; this last is a "universal output"
routine that will send to screen, printer, disk file, whatever.

If you're looking for a sudden screen change (wham!), you can build
the screen at selected addresses elsewhere in memory and then, with
suitable POKE commands, make THAT memory the screen address.

--Jim



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From Newsgroup: comp.sys.cbm

On 14 Jul 2003 08:36:33 GMT, David Mueller
<david.mueller@post.rwth-aachen.de> wrote:

- How can I display the Value of an Adress on the Screen in _decimal_?
IIRC there is some routine in the BASIC-Rom which can do this, but I'm
not sure. and reading through the Memory-Map-Document from project 64
didn't help either

Memory map? Which one? Sheldon Leemon's _Mapping the Commodore 64_ is
pretty thorough. Try LINPRT ($BDCD), which prints a number whose low
byte is in .X and whose high byte is in .A.

- What is the fastest way to put text on the screen? I think it's by
POKEing the Values right into the Scrren RAM ($0400) but I still know
there are Kernel-Routines called "CHROUT" or "STROUT" or something
like that.

Yes. CHROUT ($FFD2) prints the character in .A, STROUT ($AB1E) prints
the zero-terminated string (less than 255 characters I believe?) at the address which is stored as low byte in .A, high byte in .Y.

- How can I turn on and off the LED of the Floppy? I have seen some
Demos which do this, should be just one POKE ?

You would have to send custom programming to the drive's CPU. That's
way beyond my ken. Suggestion: Disassemble one of those demos and
rustle through it. ;)

And generally I'm looking for some complete Documentation to the
Opcodes of the 6502, even the "illegal" ones.

First, note that the C64's CPU is a 6510, not 6502. The difference is
subtle but profound. Especially if you're a daredevil using the
undefined ('illegal') opcodes. :)
Second, opcodes... wow, that's a biggie. Especially with the
undefined ('illegal') opcodes, which aren't guaranteed to work
consistently on, well, anything, including the same CPU from one moment
to the next.

Table: http://www.applefritter.com/apple1/members/pom1/Docs/m6502/6502-6510-8500-8502%20Opcodes.htm

Descriptions: http://www.applefritter.com/apple1/members/pom1/Docs/m6502/6502%20C64%20Programmer%20Guide.txt

Descriptions, including undocumented opcodes: http://www-2.cs.cmu.edu/~dsladic/vice/doc/64doc.txt http://wwwstud.ira.uka.de/~s_tomczy/opcodes.html

Be careful, and remember that a little knowledge can be a dangerous
thing. Let everyone on the newsgroup know when you code up something
cool. :)
--
Matthew W. Miller <mwmiller@columbus.rr.com>
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From Newsgroup: comp.sys.cbm

On Tue, 15 Jul 2003 23:27:44 GMT, fjb@pathcom.com (Jim Butterfield)
wrote:

(... details not included; if interested, ask).

In response to an email followup from David Mueller. Note that this
is somewhat cryptic; my posting service doesn't seem to be able to
cope with longer uploads. (Why? why?)

How can I divide a Number by ten?

Subtract ten repeatedly until the result is less than ten,
while counting the subtractions. For a 16-bit number,
subtract 10,000 repeatedly, then subtract 1000 repeatedly;
each time, you'll get a decimal digit. That's generally how
it's done in the kernal, but a general division algorithm may
be better.

I seem to remember that
dividing by two is done by just rotating ...
But I really can't remember how to do this with any number besides 2.

You're right about "two"; other numbers take a little more
coding. Here's how a general division algorithm works: Take
the number to be divided, and tack a zero byte at the high-order
end. Now shift the whole mess one bit to the left. Check the
(previously zero) byte at the top, to see if it's higher that
your divisor (ten in this case). If it is, subtract the
divisor and set the low bit in the quotient. Repeat this
shifting left, testing, subtracting if necessary, for as many
times as you have bits in the original number; be sure to
shift the quotient left each time, too. The remainder will be
in the high (originally zero) bit.

Try working this out on paper first; an elegant trick is to
put the quotient into the space the original number occupied;
thus, as the number moves out, the quotient moves in and the
single left-shift sequence does both.

And what is this algorithm, using the "decimal" mode?

Simpler, and quite astonishing. Set up a decimal (BCD) zero
result area. Now, for each bit of the argument:
-shift the whole argument one bit left; don't touch the
resulting carry bit;
-in Decimal mode, add the BCD result area to itself. You'll
be doubling the number (in BCD mode); and if the carry bit was
set, you'll also add one.
When you've done this for all the bits of the argument, the
BCD area will contain the decimal value. You'll have to split
apart the two digits in each byte, of course, for printing.

--Jim



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From Newsgroup: comp.sys.cbm

Hi Paul,

r_u_sure@mybluelight.com (Paul Rosenzweig) wrote in message news:<dda6e12f.0307141002.a239972@posting.google.com>...

David Mueller <david.mueller@post.rwth-aachen.de> wrote in message news:<Xns93B86BEA88D45davidmuellerpostrwth@baneinc.my-fqdn.de>...
Poking the screen is the fastest way to transmit data to the screen
but to get results nearly equivalent to character printing, you
need to subject character data to the following transformation:

Fill a 7 element array with the following data:

128,0,64,32,64,192,128,128

Set the subscript of the array element to the ascii value of
the character divided by 32. (Note that the zeroth element
<128> is not used and is needed only to simplfy the logic)

Exclusive OR the ascii value of the character with the
selected array element and poke the result to the screen

There is a faster way to translate pet-ascii to screencode:

asl
php
asl
plp
ror
lsr

The result should be the same as with your methode.

Franz
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From Newsgroup: comp.sys.cbm

David Mueller <david.mueller@post.rwth-aachen.de> wrote in message news:<Xns93B86BEA88D45davidmuellerpostrwth@baneinc.my-fqdn.de>...

Hi there...

I don't know if this is the right Group, but since there ist no comp.lang.6502... :)

It should be right.

I just startet again to program my c64 in Assembler (I'm quite astonished that I still know that much) and now I realize that I can't remember some very simple things:

- How can I display the Value of an Adress on the Screen in _decimal_? IIRC there is some routine in the BASIC-Rom which can do this, but I'm not sure. and reading through the Memory-Map-Document from project 64 didn't help either

Puting the value of an address on the screen if quite simple in
hexadecimal. Maybe if you use BCD it can be done the same way in
decimal? I don't have mutch expirience with BCD.

- What is the fastest way to put text on the screen? I think it's by
POKEing the Values right into the Scrren RAM ($0400) but I still know there are Kernel-Routines called "CHROUT" or "STROUT" or something like that.

You should use standard Kernel routines. I don't have my reference
book, and a am a lot off shape for C64. Basicly you put a zterminated
string in memory and then call $ffd2 :( i think, with the start
address of the text. The routine will put the text starting from
curent cursor position. You can easily modify the cursor position on
the zero-page, or by some Kernel routine.
Standard Kernel routines for puting out text are fast enuff for normal
work. You may need to write directly to the screen only when useing
raster irq's.

I don't know what you mean by Pokeing directly to screen. The basic
poke command is veeeery slow. Million time slower than sta $[address].

- How can I turn on and off the LED of the Floppy? I have seen some Demos which do this, should be just one POKE ?

Can't help.

And generally I'm looking for some complete Documentation to the Opcodes of the 6502, even the "illegal" ones.

Run a search on Goole.

Thank's a lot for your help!

David

It's not mutch of a help...

You can figure out how to do what you want quikly, just find a list of
Kernel i/o routines with a short description.

Vasko
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From Newsgroup: comp.sys.cbm

Hi Paul
r_u_sure@mybluelight.com (Paul Rosenzweig) wrote

In addition your scheme fails to match character printing
for text with PETSCII values in the range from 96 to 127. These PETSCII values are very rare. Your alternative scheme should be considered when
it is likely that only text with common PETSCII values will be encountered.

Thank you for noting that. I never realized the failure, because I use
the code-sequence for transferring keyboard input, and the keyboard
does not output ascii-values between 96 and 127 (as far I know). But
indeed, it could be a problem concerning any other input source.

Franz
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From Newsgroup: comp.sys.cbm

Hy guys

If you look for documentation about c64 asm and C64 Ml coding
tutorials, grab my huge collection:

ftp://ftp.padua.org/pub/c64/Docs/ml-tutorial.zip http://bj.spline.de/stuff/ml-tutorial.zip


Regards,
Mihai
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