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TL16C550 UART Problems

Hello, I'm having a horrific problem communicating with TI's TL16C550 UART. I'm using the UART and an RS232 (MAC3221) transceiver to communicate with my PC over a serial cable. I've successfully used this exact architecture in 3 previous designs. I'm using the exact same DSP software that I used in my previous designs. I've scoped all of the control signals of the UART and they're all doing what they should be doing. I've written all of the internal registers of the UART and read them back and they're all set to what they were set to in the previous designs. But.... I'm still not getting anything on the SOUT pin. It just sits high and doesn't budge. I have a baud rate signal coming out of the UART, but I cannot get anything on SOUT. I tried switching to a brand new board and ran my code and I got something out on SOUT for a short time (30-60 seconds) and then nothing ever again. Any ideas would be greatly appreciated. I'm stuck and just about out of ideas. Please throw any ideas out there and I'll give it a try.

Thanks, Dale

Reply to
dale.prather
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IIRC, there were lots of 550 "flavors" out there. This device has plenty of Reset and Enables (Chip selects, etc..) I'm wondering if there's a problem with those (or the PCB layout?) allowing you to still read/write but inhibiting actual throughput.

I would get the datasheet handy, and then work through all of the control pins and determine pass/fail for each. Maybe you'll get lucky?

If this is a legacy product, that you know works, maybe you just have a bad batch of chips, or have something weird going on with the power supplies, (or something else unrelated to the 550's themselves). Just a thought.

-mpm

Reply to
mpm

Thanks for your input. You make two good points. I think there's a very good chance that we had a bad batch of chips. We got a new batch and it seems to be working for the time being. Your last paragraph is also a good possibility. As of now we're getting data out of the UART and now the RS232 chip is not responding. So, we're still not getting data out to the PC.

Reply to
dale.prather

To me, the fact that you got one to work for 30 seconds and then it failed indicates that either the IC's are no good or you're doing something that blows it out... such as maybe a bad PCB layout that makes some sort of unintended connection.

Jean

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Reply to
lestrale

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