| Re: [hatari-devel] Hatari/EmuTOS Conflict |
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On 12 Jun 2013 at 23:21, Vincent Rivière wrote:
> Le 12/06/2013 21:12, Nicolas Pomarède a écrit :
> > Now, Emutos should be correct regarding the byte to expect after a soft
> > reset, and Hatari should be correct regarding the serial line's state just
> > after a cold start.
>
> Amazing analysis and bugfix!!
>
> Hatari and EmuTOS are now more accurate than ever :-)
>
Yes, really good work!
> BTW: Can we be sure that on real hardware the cold boot 0xf1 is not received
> by the ACIA?
> As I said previously, Atari TOS just waits a fixed time after sending 0x80
> 0x01. If 2 bytes arrives, I guess that it causes an receiver overrun, and no
> one notices...
> I thought that checking the RDRF bit before reading the data register was a
> good idea to do clean things, but maybe I was wrong...
> So I wonder if the current EmuTOS still works fine on cold boot on real
> hardware.
>
According to the Motorola 6850 manual:
"The ACIA contains power-on reset logic to ... hold the chip in a reset state
.... The power-on reset is released by means of the bus-programmed master reset
which must be applied prior to operating the ACIA."
So I think it's reasonable to assume that the ACIA doesn't see anything on the
data line until after the operating system does a master reset.
Roger