UCC UART Rx Clock Determination

[naveennaga]

Hi,

In the p1021 processor , we are operating QE UCC 5 in slow protocol for UART . The UART is working if the Tx & Rxclock source from internal BRG with same baud rate. Then the Rx clock is sourced from the external clock source with know frequency , same frequency is set for Tx BRG also.

If Rx clock source frequency is unknown the Tx clock rate has to be set according to the Rx clock rate received i.e how to determine the Rx clock rate before setting the Tx rate.

How we can read Rx frequency in QE UCC?

[Pavel]

The BRG setting is available using the BRG Configuration Registers 1–16 (BRGCn). See the Section 5.7 of the QE Reference Manual (https://www.freescale.com/webapp/Download?colCode=QEIWRM&location=null&fpsp=1&WT_TYPE=Reference%20Ma...) 

The UCC UART supports autobaud. Find the ATB bit in the BRGCn register. This possibility provides detect RX baud rate. If RXD goes low, the BRG determines the length of the start bit and synchronizes the BRG to the actual baud rate.

Have a great day,
Pavel

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