RE: [ECOS] Question about system bus

["HuangQiang" <jameshq at liverpool dot ac dot uk>]

-----Original Message-----
From: harri.siirtola@vtt.fi [mailto:harri.siirtola@vtt.fi]
Sent: 19 June 2001 08:36
To: HuangQiang; eCos
Subject: Re: [ECOS] Question about system bus


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).

But in the source code there "k!=1" ( I check it using the debuger). So if I
want to read a data from a memory location how can I use it?
  by "k = *EXTIOBANK0" or other means?
When I write the data to the external memory location by "*EXTIOBANK0 = 1" ,
I can get the CS signal for ext io bank0, while read I can't get the CS
signal, why? Thank you
huang



>
>Thank you
>
>huang

	Harri