Lpc2000

Hi Mouaaz,

the Rules of Bit Timing Parameters are not described in the Philips 
LPC2000 User Manuals. And they are not easy. Please refer to the 
Bosch Homepage for more Information.
But, I give you an Example that works very well in my application:

Assumed that you setup the PLL and the cclk = 60 MHz and the VPB 
Divider = 4 (after RESET) and the pclk = 15 MHz, you can use the 
following parameters for a first test:

// Common CAN bit rates for cclk=60 MHz, VPBDIV=4: ==> pclk=15 MHz:
// CAN Bit Timings in Detail -->   // SAM TSEG1 TSEG2 SJW SP%  BRP
#define CANBit10k_15MHz   0x25C095 // 0+1  5+1   2+1  3+1 70  149+1
#define CANBit25k_15MHz   0x25C03B // 0+1  5+1   2+1  3+1 70   59+1
#define CANBit50k_15MHz   0x25C01D // 0+1  5+1   2+1  3+1 70   29+1
#define CANBit100k_15MHz  0x25C00E // 0+1  5+1   2+1  3+1 70   14+1
#define CANBit125k_15MHz  0x25C00B // 0+1  5+1   2+1  3+1 70   11+1
#define CANBit250k_15MHz  0x25C005 // 0+1  5+1   2+1  3+1 70    5+1
#define CANBit500k_15MHz  0x25C002 // 0+1  5+1   2+1  3+1 70    2+1
#define CANBit1000k_15MHz 0x48C000 // 0+1  8+1   4+1  3+1 67    0+1

The following parameters for VPBDIV = 1 I have calculated on this 
base:

For cclk = 60 MHz and VPBDIV = 1, the following parameters should 
work:

// Common CAN bit rates for cclk=60 MHz, VPBDIV=1: ==> pclk=60 MHz:
// CAN Bit Timings in Detail -->   // SAM TSEG1 TSEG2 SJW SP%  BRP
#define CANBit10k_60MHz   0x25C257 // 0+1  5+1   2+1  3+1 70  599+1
#define CANBit25k_60MHz   0x25C0EF // 0+1  5+1   2+1  3+1 70  239+1
#define CANBit50k_60MHz   0x25C077 // 0+1  5+1   2+1  3+1 70  119+1
#define CANBit100k_60MHz  0x25C03B // 0+1  5+1   2+1  3+1 70   59+1
#define CANBit125k_60MHz  0x25C02F // 0+1  5+1   2+1  3+1 70   47+1
#define CANBit250k_60MHz  0x25C017 // 0+1  5+1   2+1  3+1 70   23+1
#define CANBit500k_60MHz  0x25C00B // 0+1  5+1   2+1  3+1 70   11+1
#define CANBit1000k_60MHz 0x48C003 // 0+1  8+1   4+1  3+1 67    3+1

Write this Values to the CANBTR Register.

The defined CAN Bit Rates works very well in my application (Keil 
MCB2100 connected to a CAN Analyzer (CANalyzer from vector 
informatik)).

The right Bit Rate Calculation is:

Bit rate = cclk / ( VPBDIV * BRP * ( TSEG1+1 + 1 + TSEG2+1))

The Sample Point should be in the Range 50% to 90 %.

Please download the Keil Examples for a CAN Driver, that was very 
helpful for me:

http://www.keil.com/download/docs/lpc2_can_examples.zip.asp

Greetings from Dietmar.

http://www.weiss-electronic.de

-----------------------------------------------------------------

--- In lpc2000@yahoogroups.com, "mouaaz" <mouaaz@y...> wrote:
> 
> Dear all,
> 
> I am using two LPC2129 boards having 12 MHz clock, with CCLK and 
PCLK
> set to 60 MHz. They are connected via a CAN link. I am trying to set
> the bus timing register C1BTR to run the CAN at the baudrate of 1
> Mbit/s. The value I tried is :
> 
> C1BTR = 0x34C005;
> 
> But it did not work.
> 
> Anybody can help me to work out the correct setting of this register
> to let the CAN go for 1 Mbaud.
> 
> Thanks very much.
> 
> Mouaaz
> 
> PS. the correct setting for 125 kbaud was: C1BTR = 0x001C001D;