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Microcontroller
Peripheral Timing
Calculator

SJA1000 and Philips XA-C3 - CAN baud rates

  

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For the SJA1000, the following calculators are available for the settings of the acceptance filters:

For the XA-C3, the following calculators are available for the settings of the acceptance filters:

For bus timing calculations, enter your external clock rate and the desired baud rate,
then click on the "Calculate" button

Clock frequency (in MHz): (mhz)
Desired baud rate (in kBit): (kbps)

NOTE:
CiA recommended baud rates: 10-500kBit, 800kBit or 1MBit.

CiA recommended values for entered baud rate

Description Values
Bit time (length of one bit)
(microseconds)
Number of TQ per bit
Length of TQ
(microseconds)
Sample point
Synchronization Jumpwidth
(number of TQ for sync)

The following values will only be calculated, if you entered a CiA recommended baud rate!

Register Desired Value Available Value Variance
Length of TQ
(microseconds)
(CiA)
tqa=2*(brpa+1)/mhz
=(tqa-tq)/tqa
Baud Rate Prescaler: BRP
brpd=mhz*tq/2-1
brpa=Round(brpd)		  
Number of TQ in TSEG1  
(CiA)		  
Number of TQ in TSEG2  
(CiA)		  
SJA1000: BTR0
(Sync Jump Width, BRP)		  
btr0=64+brpa		  
SJA1000: BTR1
(TSEG2, TSEG1)		  
btr1=(tseg2-1)<<4
+(tseg1-1)		  
XA-C3: BTR
(BTR0, BTR1)		  
btr=(btr1)<<8
+(btr2)		  

NOTES:
1.) Total number of TQ = 1 + tseg1 + tseg2
2.) Register value of brp, tseg1 and tseg2 = desired value - 1

Non CiA dependent values

The following values are calculated independently from the CiA recommended values above. These are not complete and can only give you an overview of possible settings.

Baud Rate Prescaler: BRP
(only first 8 values)

Length of TQ
(microseconds)

kBit Rate
(with 8 TQ,
75% SP)

kBit Rate
(with 10 TQ,
80% SP)

kBit Rate
(with 16 TQ,
87.5% SP)
0
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© ESAcademy, 2000
Author: Olaf Pfeiffer

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