it will be fine when using CY7C68013A as usb interface device
.

 
------------------ Original ------------------
From:  "Jan Smrz"<jan.smrz@volny.cz>;
Date:  Sat, Feb 16, 2013 04:18 PM
To:  "minila-forum"<minila-forum@lists.sourceforge.net>;
Subject:  Re: [Minila-forum] MiniLA USB interface

Hello,

your observation about the timing on the edge is correct. However, using
the 74HCT7053 solved the problem. Are you sure you are using 74HCF7053
and not standard CMOS HCF4053? I've not found any datasheet of the
74HCF7053. The CMOS switches have much higher switch-on resistance what
is causing timing problems. On other forums I noticed problems reported
only when using CMOS ones.

Jan



Dne 15.2.2013 21:45, Mateusz Plocinski napsal(a):
> Hello everyone,
> Yesterday I found my miniLA device which I built about 6 years. I have
> original PCBs the same as these presented on project webpage. I also
> found an USB interface original PCB and couldn't resist to mount and
> test it.
> I have a following problem, my miniLA works fine when connected to my
> older computer via LPT port. No communication problems, even with a 5m
> long cable.
> But it doesn't work with USB interface. I started to get very deeply
> into the whole thing, even looked into the source code, learned the
> EEP protocol basics, looked at the waveforms on the oscilloscope. This
> problem made me mad :).
> In my USB interface I used FT2232D which is backward compatible with
> FT2232C. I also used 74HCF4053 multiplexer because I didn't have 74HCT
> but there are no very many differences between timings of these devices.
>
> It looks like the USB interface works on the edge. Sometimes, every
> few seconds application gets a proper reading of firmware version from
> the device. But /DST and /AST signals are delayed compared to /RD,
> /WR, ALE signals because of this multiplexer which is not fast enough
> for 6MHz signals. I seems that as the result, device and PC doesn't
> latch the proper value of data bits.
> The second problem is that address write signal changes to low exactly
> the same time as /AST strobe. Shouldn't it be settled at least a clock
> cycle before /AST?
>
> I'm going to order some different versions of 4053 multiplexer and
> then compare the results, maybe a little faster IC will make it work
> without problems. I'm not sure if there are any important timing
> differences between HC. HCT, HCF, HEF versions of these devices.
>
> Or maybe a problem is somewhere else. Did anyone have similiar
> problems with USB interface?
>
> Regards,
> Mateusz SQ3PLX
>
>


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