Re: [N8VEM: 15572] Re: ECB PropTerm

[Alan Hightower <al...@alanlee.org>]

Sergey,

Have you explored maybe putting two back to back IDT720x FIFOs in front of the Prop instead?  It would eliminate any extra waits on both sides, pipeline the data transactions, and allow the EF signal to be used as an IRQ to both sides.

Something to consider for a later design.

-Alan

Sent from my iPad

On Feb 12, 2013, at 9:39 PM, Sergey <skis...@gmail.com> wrote:

> Yoda,
> 
> I was checking the possibility of re-using PropIO design before I
> designed the ParPortProp board. (I believe a schematic of that attempt
> is still somewhere on the Wiki), including the modification that
> you're suggesting here - using an SR flip-flop to put the CPU in the /
> WAIT state until propeller had processed the command and ready. And it
> has some drawbacks (unknown FF state upon reset or power on, it is
> impossible to reset propeller from the software, it adds wait
> states...).
> 
> 8255 on other hand allows a very simple decoupling of the Propeller
> from the ECB bus. PPI in this case uses mode 2 which is intended
> exactly for this purpose (and there is no bit banging necessary). It
> also can support interrupt to indicate ready to send / receive data.
> 
> This approach has been tested with Zeta SBC and runs reliably even on
> 20 MHz (of course on the ECB systems the bus will limit the
> frequency).
> 
> I don't mind designing the PCB myself. The PropIO board needs to be
> updated anyway to fix this frequency limitation issue, and to make it
> ECB/Kontron compatible.
> 
> Thanks,
> Sergey
> 
> On Feb 12, 7:49 am, yoda <y....@r2d2.org> wrote:
>> Why do we need another propIO which this is with a parallel port stuck in
>> front of it?  PropIO works reliably under 6MHz and can be made reliable
>> above that by just putting in a set/reset flipflop of the CS / enable
>> connect to the wait.  I believe there are spare NAND gates on the board to
>> do this but I have not had time to do that - seems it would be more
>> productive to implement the solution on the current board and get a re spin
>> then to make a whole new board.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On Tuesday, February 12, 2013 2:37:16 AM UTC-6, Sergey wrote:
>> 
>>> Hi,
>> 
>>> I uploaded the initial schematics for ECB PropTerm:
>> 
>>> http://n8vem-sbc.pbworks.com/w/file/63550295/ECB%20PropTerm%20-%20Sch...
>> 
>>> Basically it is a ParPortProp together with an 8255 PPI and ECB
>>> interface attached.
>> 
>>> It provides simple and reliable terminal (and also SD card storage)
>>> capabilities to ECB systems.
>> 
>>> Perhaps schematic can be simplified a bit (I think 74LS241 buffers on
>>> EBC are redundant).
>> 
>>> I'd like to get any comments and suggestions...
>> 
>>> Thanks,
>>> Sergey
> 
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