RE: [Rcxemul-discussion] Strange things afoot

[David E. <d.a...@du...>]

The error is repeatable. I tried again and exactly the same byte was
written incorrectly as 0x15. When the emulator receives a packet, for
debugging purposes I output the data in the packet, and it does indeed
read 0x1D for that particular message.

I'm attempting to get a dump of the instructions that are executed for
that byte to see if anything odd is happening there. Specifically, I
want to look at whether it's attempting to write 0x1D or 0x15 to memory.

> 0x1D may be written to the socket, but are you sure that is 
> what is coming out of the other end of the pipe?  Let's say 
> you slightly corrupt your memory (I haven't looked at the 
> code, so I don't know how you allocate memory and control 
> it), and this corruption is apparent only on this byte, 
> producing (since the program/rom is running through the same 
> sequence each
> time) a reproducable error in the socket memory buffer only 
> on this byte.
> 
> Assuming the socket recieve buffer is not corrupted, the 
> firmware buffer the final byte is added to may be.  Again, I 
> haven't looked at the code or been able to get the firmware 
> to download, so you may be printing out all recieved bytes.
> 
> This is why I hate straight C.
> 
> ----- Original Message -----
> From: "David Edwards" <d.a...@du...>
> To: <rcx...@li...>
> Sent: Friday, October 18, 2002 7:22 PM
> Subject: [Rcxemul-discussion] Strange things afoot
> 
> 
> > I'm hot on the trail of the reason why the firmware won't 
> unlock. I've 
> > discovered that the last time I tried it, there was only 
> one byte in 
> > the entire firmware transferred wrongly. This put the 
> checksum off by 
> > 8:
> >
> > Expected
> > 0xA000 77 79 1E 11 1E 88 1E 00 0D 42 1D 20 47 1E 6E 6A
> >
> > Observed
> > 0xA000 77 79 1E 11 1E 88 1E 00 0D 42 15 20 47 1E 6E 6A
> >
> > Note that we have 1D in the expected firmware image, and 15 in the 
> > observed. I have no idea why! I've traced through the tons of debug 
> > information that I have and I'm still at a loss. 0x1D is definitely 
> > the value that gets transmitted by the firmware downloader, 
> but 0x15 
> > is being written.
> >
> > I'm going to try again to see if it's the same byte that 
> gets written 
> > wrongly. If it is, I'm going to have to trace the receive 
> handler for 
> > that particular byte to see why it's not getting set correctly.
> >
> >
> >
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