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Problem in External Memory Interface in C8051F120

Rajesh N

Hi,

I am using C8051F120 from Silabs.., I have connected PPI 8255 with my controller which is be addressed as External Memory interface(EMI) as I take control lines of PPI A0,A1 with lower ports of Microcontroller..

I am finding problem with interfacing using XBYTE to address externaly..,

Ex:


   XBYTE[0x0000]=0xFF;

where the control lines of PPI A0,A1 r selected with address XBYTE[0x0000] and data is latched with 0xFF;

this operation is not performed properly..,

If there is any solution to this problem.. plz let me know...

Rajesh

Parents
  • 0 in reply to Andy Neil

    this operation is not performed properly

    Of course it is not! Would a tire for a Ford T work with a Mustang Cobra?

    Instead of posting "how do I use this antique" post "how do I make so and so"

    1) you have 8 ports, WHY ON EARTH do you bring in this antique
    2) If you HAVE TO use this old, outdated, antique chip, then instead of using the f120 to the full extent SLOW IT DOWN TO A CRAWL (to match a 8255 you will, probably, need to clock at not 100, but one MHz).

    Throw the blasted 8255 out and post what you are trying to do and the 'how' will be forthcoming.

    a general note: read the timing specifications in the datasheets before hooking components together.

    Erik

Reply
  • 0 in reply to Andy Neil

    this operation is not performed properly

    Of course it is not! Would a tire for a Ford T work with a Mustang Cobra?

    Instead of posting "how do I use this antique" post "how do I make so and so"

    1) you have 8 ports, WHY ON EARTH do you bring in this antique
    2) If you HAVE TO use this old, outdated, antique chip, then instead of using the f120 to the full extent SLOW IT DOWN TO A CRAWL (to match a 8255 you will, probably, need to clock at not 100, but one MHz).

    Throw the blasted 8255 out and post what you are trying to do and the 'how' will be forthcoming.

    a general note: read the timing specifications in the datasheets before hooking components together.

    Erik

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