From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <008201c07eec$52fd7da0$4a1f76d8@washington> From: "Navin Boppuri" To: "Linux PPC embedded" References: <003b01bfbc02$88afc3c0$4a1f76d8@washington> <3A5FBDC0.6785393F@brainlink.com> Subject: Re: UART configuration problems Date: Mon, 15 Jan 2001 12:11:43 -0000 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Hello Ormund, >>From your mail, I can make out that you worked on the MAX3100 uart before. Can you please tell me how I can do a read from the buffer? I am confused as to how to read the buffer without overwriting it with the following data. How much delay is the right delay? Please help, I am kinda stuck here. Thank you, Navin Boppuri ----- Original Message ----- From: "Ormund Williams" To: "Linux PPC embedded" Sent: Saturday, January 13, 2001 2:30 AM Subject: Re: UART configuration problems > > 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/