MCF8252 UART using interrupts for Rx
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MCF8252 UART using interrupts for Rx
by Victor Remete
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From: Victor Remete <vremete@...> To: coldfire@... Subject: MCF8252 UART using interrupts for Rx I would like to use the UARTs in the MCF8252 using interrupts. How do I program the UART for reception so that I get an interrupt 1. when the Rx FIFO is 3/4 full (trigger level), or 2. if no character is received for N character times (timeout, where N=4 in the National Semiconduction NS16550, but I am not picky on the value of N as long as it is 2 or more). ------------------------------------- --- coldfire@... Send a post to the list. coldfire-join@... Join the list. coldfire-digest@... Join the list in digest mode. coldfire-leave@... Leave the list. |
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Re: MCF8252 UART using interrupts for Rx
by Marc Vincent-3
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Hi Victor.
The MCF5282 UARTs don't have a 16-deep FIFO like the 16550; you don't get interrupts based on FIFO 3/4 full. If you enable RX ints, you get an IRQ as soon as the first incoming character is transfered from the shift register to the receive data buffer. The receive FIFO is 4-deep, so your interrupt latency has to be less than 4 x (#bits/char) / baudrate. You also don't get a "receive timeout" interrupt, this is not a 68302 or a QUICC :-( On the other hand, if you know the expected receive buffer length, you can program a DMA channel to retrieve characters from the UART's receive data buffer on a RX event and get interrupted at the end of the DMA transfer. Hope this helps. Marc Vincent PS: I'm assuming you're at siamtec. If so, pls say SALUT to Pierre M. for me and have him give me a shout if any of this does not make sense. You may remember me or not, I'm a STAS and NTC alumni... On Mon, Jun 30, 2008 at 2:57 PM, Victor Remete <vremete@...> wrote: > -------------------------------------------------------------- > From: Victor Remete <vremete@...> > To: coldfire@... > Subject: MCF8252 UART using interrupts for Rx > > I would like to use the UARTs in the MCF8252 using interrupts. > How do I program the UART for reception so that I get an interrupt > 1. when the Rx FIFO is 3/4 full (trigger level), or > 2. if no character is received for N character times (timeout, > where N=4 in the National Semiconduction NS16550, but I am > not picky on the value of N as long as it is 2 or more). > > ------------------------------------- > > > --- > coldfire@... Send a post to the list. > coldfire-join@... Join the list. > coldfire-digest@... Join the list in digest mode. > coldfire-leave@... Leave the list. > > coldfire@... Send a post to the list. coldfire-join@... Join the list. coldfire-digest@... Join the list in digest mode. coldfire-leave@... Leave the list. |
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Re: MCF5482 UART using interrupts for Rx
by Marc Vincent-3
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On Wed, Jul 2, 2008 at 2:05 PM, Victor Remete <vremete@...> wrote:
> Sorry, > > I had the wrong processor number in my original post. > It should be MCF5482 not MCF8252. Ok, I thought you meant the MCF5282. The serial ports are completely different on the 548x. > How do I program the UART for reception so that I get an interrupt > 1. when the Rx FIFO is 3/4 full (trigger level), or 1- Set PSCMR1n bit 6 (FU) to get interrupted when RxFIFO count > threshold 2- Set the RxFIFO alarm in PSCRFARn bits 0-8. For 3/4 full: 512 - 512*3/4 = 128 > 2. if no character is received for N character times (timeout, > where N=4 in the National Semiconduction NS16550, but I am > not picky on the value of N as long as it is 2 or more). The PSC does not do that. You need to use a soft or hard timer and poll RXRDY (PSCSR bit 8). Marc --- coldfire@... Send a post to the list. coldfire-join@... Join the list. coldfire-digest@... Join the list in digest mode. coldfire-leave@... Leave the list. |
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