8085 simulator in C

[activearun.83]

Hi everyone,

Can anyone give some idea about developing an 8085 simulator
program in C? What techniques can be handled to develop this?

[Walter Roberson]

In article <11************ **********@x35g 2000prf.googleg roups.com>,
ac***********@g mail.com <ac***********@ gmail.comwrote:

Can anyone give some idea about developing an 8085 simulator
program in C? What techniques can be handled to develop this?

-Personally-, I wouldn't bother unless it was an assignment or
a pet learning project (and even then, I'd reconsider whether
8085 was the right choice of processors.)

If you wanted an 8085 simulator, I'd look around and try out
http://sourceforge.net/projects/sim85
or Vaneet Singla's 8085 simulator (available in a wide variety of places)
--
If you lie to the compiler, it will get its revenge. -- Henry Spencer

[user923005]

On Jun 4, 11:15 am, "activearun...@ gmail.com"
<activearun...@ gmail.comwrote:

Hi everyone,

Can anyone give some idea about developing an 8085 simulator
program in C? What techniques can be handled to develop this?

http://www.google.com/search?hl=en&q...=Google+Search

[mstorkamp]

On Jun 4, 1:30 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:

In article <1180980953.503 669.203...@x35g 2000prf.googleg roups.com>,

activearun...@g mail.com <activearun...@ gmail.comwrote:

Can anyone give some idea about developing an 8085 simulator
program in C? What techniques can be handled to develop this?

-Personally-, I wouldn't bother unless it was an assignment or
a pet learning project (and even then, I'd reconsider whether
8085 was the right choice of processors.)

I don't think 8085 is such a bad choice. Very simple instruction set.
I did this one weekend about 20 years ago just for the heck of it. I
had an old single board PC I wanted to emulate on a VAX.

The OP wanted suggestions on techniques to do this. As I recall, the
upper nibble of the opcode pretty much tells you what the instruction
will do, so I made an array of 16 functions and used the upper nibble
to index into the array. Then I had 16 individual functions to handle
the operations. The lower nibble is mostly for addressing, so that too
can index into an array for the correct register. Setting the flags
properly was the trickiest part.

[Ben Pfaff]

ms*******@yahoo .com writes:

The OP wanted suggestions on techniques to do this. As I recall, the
upper nibble of the opcode pretty much tells you what the instruction
will do, so I made an array of 16 functions and used the upper nibble
to index into the array. Then I had 16 individual functions to handle
the operations. The lower nibble is mostly for addressing, so that too
can index into an array for the correct register. Setting the flags
properly was the trickiest part.

This sounds like a fun instruction set on which to practice
writing a (static or dynamic) binary translator. (Of course,
there's no way to actually run the translated code without
invoking undefined behavior, from a comp.lang.c point of view.)
--
Ben Pfaff
http://benpfaff.org

[Chris Hills]

In article <11************ *********@w5g20 00hsg.googlegro ups.com>,
ms*******@yahoo .com writes

>On Jun 4, 1:30 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:

>In article <1180980953.503 669.203...@x35g 2000prf.googleg roups.com>,

activearun...@ gmail.com <activearun...@ gmail.comwrote:

Can anyone give some idea about developing an 8085 simulator
program in C? What techniques can be handled to develop this?

-Personally-, I wouldn't bother unless it was an assignment or
a pet learning project (and even then, I'd reconsider whether
8085 was the right choice of processors.)

I don't think 8085 is such a bad choice.

It is if you want o buy one... I am certain the are obsolete these
days,.

Very simple instruction set.
I did this one weekend about 20 years ago just for the heck of it. I
had an old single board PC I wanted to emulate on a VAX.

Exactly....20 years ago It might be technically nice but getting the HW
is another matter. As for the tools.... i will dust of the compiler on
the 5.25" floppies.....

--
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
\/\/\/\/\ Chris Hills Staffs England /\/\/\/\/
/\/\/ ch***@phaedsys. org www.phaedsys.org \/\/\
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/

[mstorkamp]

On Jun 5, 10:45 am, Chris Hills <c...@phaedsys. orgwrote:

In article <1181057388.694 969.70...@w5g20 00hsg.googlegro ups.com>,
mstork...@yahoo .com writes>On Jun 4, 1:30 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)

wrote:

In article <1180980953.503 669.203...@x35g 2000prf.googleg roups.com>,

activearun...@g mail.com <activearun...@ gmail.comwrote:
Can anyone give some idea about developing an 8085 simulator
program in C? What techniques can be handled to develop this?

-Personally-, I wouldn't bother unless it was an assignment or
a pet learning project (and even then, I'd reconsider whether
8085 was the right choice of processors.)

I don't think 8085 is such a bad choice.

It is if you want o buy one... I am certain the are obsolete these
days,.

Very simple instruction set.
I did this one weekend about 20 years ago just for the heck of it. I
had an old single board PC I wanted to emulate on a VAX.

Exactly....20 years ago It might be technically nice but getting the HW
is another matter. As for the tools.... i will dust of the compiler on
the 5.25" floppies.....

You can still get the Z80 at DigiKey. Same instruction set, even
easier to connect up (the address and data bus are not multiplexed
like on the 8085). But then the OP just wants to emulate it, not build
one (but I would suggest doing so anyway). And since he wants to do it
in C, if he has trouble along the way his questions will likely be on
topic for this group. As to the rest of this discussion...

[Jean-Marc Bourguet]

ms*******@yahoo .com writes:

You can still get the Z80 at DigiKey. Same instruction set, even
easier to connect up (the address and data bus are not multiplexed
like on the 8085).

I think you are confusing 8080 and 8085.

--
Jean-Marc, who has programmed both but could be the one doing the confusion

[mstorkamp]

On Jun 5, 11:28 am, Jean-Marc Bourguet <j...@bourguet. orgwrote:

mstork...@yahoo .com writes:

You can still get the Z80 at DigiKey. Same instruction set, even
easier to connect up (the address and data bus are not multiplexed
like on the 8085).

I think you are confusing 8080 and 8085.

--
Jean-Marc, who has programmed both but could be the one doing the confusion

Nope, the 8080 used an external clock generator (8224) and system
controller (8228) that were built into the 8085. There are a couple of
undefined opcodes in the 8080/8085 that the Z80 defined to extend the
architecture of the 8080/8085. It doubled the number of registers,
demuxed the IO, and added a few new registers. However, as long as you
don't use those undefined opcodes, it is 100% software compatible
(only the timing is different).

[Kenneth Brody]

Ben Pfaff wrote:

>
ms*******@yahoo .com writes:

The OP wanted suggestions on techniques to do this. As I recall, the
upper nibble of the opcode pretty much tells you what the instruction
will do, so I made an array of 16 functions and used the upper nibble
to index into the array. Then I had 16 individual functions to handle
the operations. The lower nibble is mostly for addressing, so that too
can index into an array for the correct register. Setting the flags
properly was the trickiest part.

This sounds like a fun instruction set on which to practice
writing a (static or dynamic) binary translator. (Of course,
there's no way to actually run the translated code without
invoking undefined behavior, from a comp.lang.c point of view.)

How so? You have a struct holding the emulator's CPU registers, and a
64K unsigned char array (or two 32K arrays, since I seem to recall the
standard not requiring support for 64K arrays) representing the memory.

Now, emulating the hardware which might be surrounding the CPU is
another story. (Though you're probably more likely to run into
"implementa tion defined" or "unspecifie d" behavior than actual UB.)

:-)

--
+-------------------------+--------------------+-----------------------+
| Kenneth J. Brody | www.hvcomputer.com | #include |
| kenbrody/at\spamcop.net | www.fptech.com | <std_disclaimer .h|
+-------------------------+--------------------+-----------------------+
Don't e-mail me at: <mailto:Th***** ********@gmail. com>