🚀 go-pugleaf

Ignac Kolenko <electro!electro!ignac@ucbvax.Berkeley.EDU> asks:

>      i have a question regarding the exact function of the upper data/lower
>data strobes on the m68k. can the LDS be used in place of the missing A0 line?

Yes, that works.

>also, if the above is correct, can i do the following:
>
>MOVEA.L $FB0000,A0
>TST.B (A0,D0.W)

Sure.

>  case anyone is wonderin' why i'm asking, i want to try to build an interface
>to my atari 1040st cartridge port, which doesn't have write access capability.
>i therefore have to use the bottom 8 lines of the address bus as a "data bus"
>when i want to write to the cartridge port address space, and using one of the
>higher address lines a pseudo read/write line. (...)

This is exactly the way all those cartrige port boards sold commercially and
offered in magazine projects do the trick.

People have used this kind of I/O interface for all kinds of stuff, from con-
trolling a robot arm to hooking up a PC-style hard disk.

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