FPU and DMA with 68000
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Author:  Dajgoro [ Thu Oct 20, 2011 12:44 am ]
Post subject:  FPU and DMA with 68000


I have already done a 6502 sbc, and now i am building a 68000 sbc, with a dma, and fpu. Since i am using a 68000 and not a 68020, the 68881 does not work like usual...
I've seen some of you have experience with the fpu, so how do i make the subroutines/macros for the fpu? And for the DMA(MC68450L10)?
The fpu is more problematic to me...

Author:  clive [ Thu Oct 20, 2011 3:12 pm ]
Post subject: 

The macro's can be found in MACRO881.ZIP
http://www.programmersheaven.com/downlo ... nload.aspx

The app note associated with it is here
http://www.retro.co.za/68000/MotorolaPD ... 7_REV0.PDF

For the DMA, you're pretty going to have to read through the documentation and program the registers appropriately. That or find some existing board or computer that uses one and look at the software. Or look at some of the more integrated 68K parts that had DMA on-chip, and implemented in a similar fashion.

Author:  Dajgoro [ Thu Oct 20, 2011 7:36 pm ]
Post subject: 

Thanks for the link!
Is there an simple example program that uses this macros?

Author:  clive [ Fri Oct 21, 2011 2:40 pm ]
Post subject: 

Dajgoro wrote:
Is there an simple example program that uses this macros?

The PDF kind of describes the expected syntax. Personally I'd think you'd want to attack this by implementing a real 6888x program, understand that, and then translate it into the macro equivalent implementation.

I haven't looked at the mechanics of the macros, but am familiar with the the 6888x co-processor protocol (instruction decode state machine), and 6888x code.

Take a look at IDE68k, it's a compiler/assembler/simulator, much like EASy68K, but capable of 68020/6888x code development. Peter Fondse did a very good job with this, and during validation I only found one issue with it and that was fixed very promptly.


Would some general 6888x code be useful? as I don't think I can readily simulate/emulate a 6888x attached to a 68000.

You might want to Google about to see if there is any code or libraries related to the 68881 co-processor board Atari made for the ST. Perhaps there are some demo-scene examples out there.

Author:  Dajgoro [ Fri Oct 21, 2011 8:58 pm ]
Post subject: 

I already tested the ide68k with the fpu, but it is strange, when i select the 68020 or the 68000 i always get the same code... A bit fuzzy...
I already searched on Google, but i didn't find much...

I would be happy to find a program in which i can input the fpu address, and the the program does some operations, like move, sine, cosine, ect... just to understand how to implement the macros and how to use them (i am new with the 68k, i know 6502 and ARM assembly).

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