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LPUART FIFO size?  Only seems to be 4 words.

Question asked by Frederick Soo on Aug 21, 2017
Latest reply on Oct 17, 2017 by Frederick Soo

hello,

 

I'm setting the LPUART FIFO RX and TX sizes and it only seems to be 4 words (0b001) and cannot be set to any other value.  In the RM it says that it can be up to 256 words (up to 0b111).  I've verified that I can set the RXFE, RXTE and RXIDEN bits properly. 

 

// disable transmit and receive so can set FIFO

LPUART1->CTRL &= !( LPUART_CTRL_TE_MASK | LPUART_CTRL_TE_MASK);

// set fifo - 1 word RX, 32 dataword TX, TX and RX FIFO enabled, 1 byte idle before RDRF transmit

LPUART1->FIFO = LPUART_FIFO_RXFIFOSIZE(0b000) | LPUART_FIFO_TXFIFOSIZE(0b100) | LPUART_FIFO_TXFE(0x01) | LPUART_FIFO_RXFE(0x01) | LPUART_FIFO_RXIDEN(0x01);

 

When I check with debugger, only RXFE, RXTE and RXIDEN bits are set, the RXFIFOSIZE and TXFIFOSIZE are both 0b001 (both starting values and after trying to set).

 

Does the LPUART support FIFO depths of anything besides 4 words?

 

best,

Fred

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