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imx28 AUART Baudrate / Hispeed /clock

Question asked by wolfgang gaerber on Mar 23, 2016
Latest reply on Mar 24, 2016 by Yuri Muhin



We (want to) use AUART module with 3.25MBs - as this is indicated as maximum speed in the reference manual p.1937.

According to this manual p.1939 - the proper divisor is:

24M x 32 / 3250000 = 236 = 0xEC - the smallest divisor allowed.

Writing this divisor in BAUD_DIVFRAC and BAUD_DIVINT - we got the following behaviour:

TX operates on any divisor setting between dec. 224 - dec 239 wiht 3.4MBps.

It really looks like the lowest 4 Bits of BAUD_DIVFRAC have no influence on the TX clock.

Otherwise it seems that this bits are used for RX clock - and then it makes a difference.

1.) Is there a document which describes TX clock / RX clock in detail ?

2.) There are 2 indications of a "HISPEED" mode in the manual - and a bit which gives details  in the status register.

Is there a document describing HISPEED mode ?