--- In motoroladsp@y..., "Johnson, Jerry" <jljohnson@g...>
wrote: > FYI: > I am using the 56F807 chip, without the type of problem you observe. I am > running at 1Mbps off of the internal clock. > > It sounds as though you have a bit rate problem, since more bytes in the > block will cause any clock skew to be more noticable. > > Since the Ack is at the end of the message, It may not be timed properly in > the presence of severly mismatched clocks. > > Is the Synchronization Jump Width set to Maximum??? > > Are you sure the internal clock is set to 40Mhz? The SDK seems to default > it to 36Mhz??? The External RAM target in SDK stationery has a default PLL multiplier of 18, producing a clock of 72 MHz and 36 MIPs performance. The FLASH target in SDK stationery has a default PLL multiplier of 20, producing 80 MHz and 40 MIPs. > For an internal clock of 40Mhz and bit rate of 1Mbps I am using: > > // for SJW = 3 (skip=4) and quanta size of 1/20 microSec (prescaler = 2) > #define CANBTR0_VALUE 0xc1 > // for 1 sample and tseg1 = 12 and tseg2 = 7 (there is one additional quanta > required for the Sync_Seg). > #define CANBTR1_VALUE 0x6B > > Hope this helps! > > Jerry. > > -----Original Message----- > From: rogergill_99 [mailto:rogergill_99@y...] > Sent: Wednesday, September 04, 2002 11:16 AM > To: motoroladsp@y... > Subject: [motoroladsp] Problem with sending 7 and 8 Byte Frame in CAN > With my target board, and the DSP56F803 Evaluation board, I am > experiencing problems with the MSCAN module when sending 7 and 8 byte > frames. > > The problem I have is when I send 7 byte frames, often I do not get > an ACK sequence from other connected devices, and when I send an 8 > byte frame, I never get an ACK sequence. This causes the MSCAN > module to resend the frame forever. > > Running at 6 byte frames down to zero byte frames does not seem to > show this problem. > > I am running the CAN at a scope verified rate of 125kbps. I was > running the MSCAN clock off the IPBUS (40 mhz) but after reading that > the PLL might have too much clock jitter, I have reverted to the 8MHZ > on board crystal oscilator. Both clock sources acted the same. > > The details for the sampling are: > TSEG1 = 13 > TSEG2 = 2 > 1 Sample > CAN BAUD Divider = 4 > > I would appreciate any help with this problem. > > Roger > <http://rd.yahoo.com/M"8862.2128520.3581629.2225242/D=egroupweb/S 057718 > 55:HM/A82709/R=0/*http://adfarm.mediaplex.com/ad/ck/990-1736- 1039-334> > > > _____________________________________ > Note: If you do a simple "reply" with your email client, only the author of > this message will receive your answer. You need to do a "reply all" if you > want your answer to be distributed to the entire group. > > _____________________________________ > About this discussion group: > > To Join: motoroladsp-subscribe@y... > > To Post: motoroladsp@y... > > To Leave: motoroladsp-unsubscribe@y... > > Archives: http://www.yahoogroups.com/group/motoroladsp > <http://www.yahoogroups.com/group/motoroladsp> > > More Groups: http://www.dsprelated.com/groups.php3 > <http://www.dsprelated.com/groups.php3 > ">http://docs.yahoo.com/info/terms/> . |