[En-Nut-Discussion] Memory mapped device

[Harald Kipp]

Carlos,

The ATmega128 data sheet will answer your questions in
great detail. You can safely modify the specific CPU
registers at the beginning of your application's main()
routine or during initialization of your driver code.
Nut/OS doesn't need to be aware of.

Harald

At 16:23 05.04.2005 +0200, you wrote:
>Hello,
>
>I have just read this thread about memory mapped devices, and as I'm using
>a CPLD, which I interface using the memory map, I would like to know 2
>things:
>
> >
> > Best use 0xD000-0xDFFF for high speed I/O and
>
>What does "high speed" exatly mean? How many ns from when the read
>instruction is executed till the data bus is latched in the micro? Is it 1
>clock cycle? If it is one cycle, and the clock is approximately 14 MHz,
>then 71'5 ns?
>
> > 0xE000-0xEFFF for low speed with optional wait
> > states.
>
>If we read and write using this addresses, how can we add wait states? Is
>there any specific instruction in NUT/OS?
>
>Thank you in advance and regards,
>Carlos.