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Re: Question about system bus
- To: "HuangQiang" <jameshq at liverpool dot ac dot uk>, "eCos" <ecos-discuss at sources dot redhat dot com>
- Subject: Re: [ECOS] Question about system bus
- From: harri dot siirtola at vtt dot fi
- Date: Tue, 19 Jun 2001 10:35:59 +0300
At 17:31 18.6.2001 +0100, HuangQiang wrote:
>Hi all:
>...
>e.g.
> reading from the ext IO
>
> int k;
> *EXTIOBANK0 = 1;
> k = *EXTIOBANK0;
> // now k is not the same as what I have written to ('1'). why ?
I don't know of EB7T exactly but in many processors, an I/O port defined as
an output is write-only. So you must maintain a static variable to hold the
last value written to the port. You said you're getting proper select
signals so I suppose your EXTIOBANK0 declaration is ok (otherwise the first
thing to check).
>
>Thank you
>
>huang
Harri