Updated UART

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Updated UART

Postby Chris » Tue Apr 30, 2013 8:02 pm

Hi,

While trying to source the needed parts I found a modern drop in replacement for the MC68681 UART. Its the NXP-SCC68692.
Seems to be generally available from digikey and farnell (p/n 1294827) for around 6 GBP.

Regards

Chris
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Re: Updated UART

Postby simon » Thu May 02, 2013 9:01 am

Hi Chris,

that are good news. Thanks for sharing this! :)
Is the device full compatible or does it provide some improvements? Better speed, bigger fifo...?

Regards
Simon
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Re: Updated UART

Postby Chris » Thu May 02, 2013 10:43 am

The baud rates seem to be the same although the spec sheet states 22 rates I can only find the same as the 68681, i think they are interpreting the original spec of the 68681 differently
It has a few extra modes such as recieve timeouts and powerdown. Other than that is is pretty much the same, timing seems compatible but sorry the FIFOs are no deeper than the 68681 :cry:

Regards

Chris
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Re: Updated UART

Postby simon » Fri May 03, 2013 4:02 pm

Sounds good though. At least because it is not obsolete. :) The fifo issue isn't that important as there is mass storage. One would want to implement something like x/y/z-modem though. :) Thanks Chris!

Simon
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Re: Updated UART

Postby mk279 » Wed Apr 16, 2014 9:29 am

Hi Chris & Simon,

sorry for reopening this oldish topic.
But in my 68k project I recently used an even more advanced UART.
It's the SC28L92 by NXP which is an enhaced 68681 with 16 bytes of TX/RX FIFOs (http://www.nxp.com/documents/data_sheet/SC28L92.pdf)
Thus, it's especially usefull to lower interrupt load on higher data rates like 57600 or 38400.
I bought mine at mouser (part number 771-SC28L92A1A529).

Regards,
Martin
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Re: Updated UART

Postby simon » Wed Apr 16, 2014 9:32 am

Hi Martin,

sounds good too me. :) Is it compatible to the MC68681? Unfortunately I already have the MC68681 for the upcoming kit in stock. But well, it's a tinkering project, thus everybody might replace it on their own. :)
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Re: Updated UART

Postby mk279 » Wed Apr 30, 2014 6:20 pm

Yes it's compatible to 68681. The initialization values of the registers match 68681 configuration.
Furthermore the pinout can be mapped to the 68681 pinout, where an additonal pin (I/M) needs to be grounded for selecting the 68xxx mode.
Unfortunately it's just available with PLCC, QFP, and HVQFN package. I build myself a DIL to PLCC adapter in order to be able to use it as drop-in replacement.
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