From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3A5FBDC0.6785393F@brainlink.com> Date: Fri, 12 Jan 2001 21:30:24 -0500 From: Ormund Williams Reply-To: Linux PPC embedded MIME-Version: 1.0 To: Linux PPC embedded Subject: Re: UART configuration problems References: <003b01bfbc02$88afc3c0$4a1f76d8@washington> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Navin Boppuri wrote: > > Hello everyone, > > I am trying to interface a MAX3100 uart to an SPI controller on the MPC823. > I have a functional SPI driver running. The transmit part of the UART works > just fine. I am able to transmit characters at 9600 8N1 baud. The problem > arises when I do a receive. The uart documentation says that the internal > fifo is 8 word long. But I notice that the FIFO is able to store only 8 > characters. For example, if I transmit the characters > abcdefghijklmnopqrstuvwxyz > > The uart shows only "yz" in its buffers. The other 24 characters are lost. I > noticed that 8 charaters are written in the buffer. It first writes > "abcdefgh" and then overwrites that with "ijklmnop" and so on. The uart > generates an irq interrupt whenever there is incoming data. I do not see why > the buffer is not big enough. > The MAX3100 is working as designed, the 8 word fifo can only hold 8 characters the other bits in the word hold the parity, framing error, etc. If the fifo overflows all characters are lost. The following is from page 5 and 7 of the datasheet. "Read data from a 16-bit register that holds the oldest data from the receive FIFO, the received parity data, and the logic level at the CTS input pin. This register also contains a bit that is the framing error in normal operation and a receive-activity indicator in shutdown." "Receive data is stored in an 8-word FIFO. The FIFO is cleared if it overflows." > Can someone give me some insight into this problem? What do I need to do to > correct this? > Read the data before the fifo overflows. -- Ormund ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/