Re: Message to Yoda re the Propeller project

[yoda <yo...@r2d2.org>]

James,

Think of the propeller as a super programmable I/O chip.  I can decide
on what the protocol I want.  For example for the keyboard and vga it
will look much like a UART to the Z80.  I will define a status
register that can be checked to see if there is a character from the
keyboard and I can have a busy status while the propeller is doing the
output to vga, etc.

There is a very nice instruction in the propeller that is called
WAITPEQ or WAITPNE  which stands for Wait for Pin(s) equal or Wait for
Pin(s) not equal.  So if you look at the schematic I have a CS, RD and
A0 and A1 going into the propeller (maybe it was WR, I don't remember
but you only need one of them).  So by keying on CS going low and
looking at A0,A1 and the RD or WR I can tell which I/O port the Z80 is
trying to read or write.  Then from that I either output the correct
data or read the data and take action.  The tricky part is that I have
~450 nsec to do this.  That is approximately 35 clocks on the
propeller so I have to be very efficient.  This part of the code will
probably be in PASM.  I can use the status register to throttle the
rate of I/Os if necessary so the rest of the code probably can be in
SPIN.  My only concern is I think I am going to have to use a hub
address for the status to communicate between Cogs and this could take
up to 17 clocks to read based on where the hub access pointer is when
a request a read from the hub memory.  I am looking at ways to split
the status up and keep it private to the Cog to eliminate this non
deterministic behavior.

Dave

On Jun 17, 11:47 pm, "James Moxham" <mox...@internode.on.net> wrote:
> That sounds intriguing. OUT and IN would be the simplest interface system.  
> Do you OUT a data byte and a command byte or something like that? To one  
> OUT address with a sequence, or to several addresses?
>
> The prop runs fast. I don't understand the prop very well, but can you set  
> a cog going so it can wait for certain pin combinations that correspond to  
> an OUT or an IN and then change the status of the data pins accordingly?  
> Does this need to exploit the timing differences between IORQ and RD (or  
> WR)?
>
> If you almost have all the pieces together, maybe this could be turned  
> into a board??
>
> Cheers
>
> James
>
>
>
> On Thu, 18 Jun 2009 13:42:09 +0930, yoda <y....@r2d2.org> wrote:
>
> > James,
>
> > Take a look at the photos and schematics - there is an SD interface on
> > my propIO board.  I have the propeller side of all the I/O (vga,
> > keyboard and SD) working - just working on the data bus side.  I use
> > the PockeTerm code for the keyboard and vga.  I have been able to talk
> > to the propeller using basic OUT and INP functions so it is really
> > putting all the pieces together.  I think the disk interface will be
> > pretty straightforward.  I am using the same technique that Cluso and
> > Heater have used for the files on the SD (actually had done
> > independently before I saw their code - great minds think alike :)  If
> > work would slow down a little and I get highly motivated for about 2
> > days I can knock this out.  See what I can do late this week or the
> > weekend - the code is all coded in my mind - just need to do a mind
> > dump and some debugging.
>
> > Dave
>
> > On Jun 17, 10:07 pm, "James Moxham (Dr_Acula)"
> > <mox...@internode.on.net> wrote:
> >> There are some great photos and a schematic on the wiki in the folder
> >> DWM-PropIO. I was wondering how this project is going? The prop is
> >> interfacing via the data bus and a few address lines, which should
> >> make for much faster IO than using serial (to the PockeTerm). I'm
> >> wondering whether this could be used to interface the sd card on the
> >> prop? I can think of three different protocols - access FAT16 files
> >> (compatible with a PC), access raw records and sectors (compatable
> >> with CP/M), or Cluso's system where you create a single file disk
> >> image using the simh, and then read it as CP/M files.
>
> >> Anyway, if the prop expansion board project is growing and it is
> >> working maybe down the track maybe we could turn this into a PCB? I'd
> >> be most interested to hear how it is progressing.
>
> --
> Dr James Moxham
> Belair Family Health Centre
> 459 Belair Rd, Belair, South Australia
> 5052
> Phone: 61+8+8278 8900
> Fax: 61+8+8370 3499
> mox...@internode.on.net
>
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