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Altera_Forum
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20 years ago

Nios-II SOPC UART delivers wrong bytes

We use the UART in our Nios-II design that comes with Quartus 5.0SP1 and Nios-II 5.0 We face the problem that sometimes the Uart reports wrong RX Bytes from correct RX streams. The serial str...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
20 years ago

If you're getting an 0x04 when you expect an 0x02, that sounds like a timing problem, like the UART is picking the wrong spot to sample the bit (or maybe there's a slow edge rate on the driver/receiver?), or is set to a close but incorrect rate (SOPC builder clock rate not the same as the real system's?).

I don't see much choice for you aside from looking at the receive signal at or near the FPGA pin, and if that looks perfect, start probing some signals inside the UART with SignalTap.