38.7.7 Nominal Bit Timing and Prescaler

This register is write-restricted and writable only if both CCCR.CCE bit (CCCR <1>) and CCCR.INIT bit (CCCR <0>) are set.

The CAN bit time may be programmed in the range of 4 to 385 time quanta. The CAN time quantum may be programmed in the range of 1 to 512 GCLK_CANx periods. tq = (NBRP + 1) mtq.

Therefore the length of the bit time is [NTSEG1 + NTSEG2 + 3] tq, where NTSEG1 and NTSEG2 are programmed values in the NBTP register.

Note: With a CAN clock (GCLK_CANx) of 8MHz, the reset value 0x06000A03 configures the CAN for a bit rate of 500 kBits/s.
Table 38-24. Register Bit Attribute Legend
SymbolDescriptionSymbolDescriptionSymbolDescription
RReadable bitHCCleared by Hardware(Grey cell)Unimplemented
WWritable bitHSSet by HardwareXBit is unknown at Reset
KWrite to clearSSoftware settable bit
Name: NBTP
Offset: 0x1C
Reset: 0x00000A33
Property: Write-restricted

Bit 3130292827262524 
 NSJW[6:0]NBRP[8] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00000110 
Bit 2322212019181716 
 NBRP[7:0] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00000000 
Bit 15141312111098 
 NTSEG1[7:0] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00001010 
Bit 76543210 
  NTSEG2[6:0] 
Access R/WR/WR/WR/WR/WR/WR/W 
Reset 0000011 

Bits 31:25 – NSJW[6:0] Nominal (Re)Syncronization Jump Width

ValueDescription
0x00 - 0x7FValid values are 0 to 127. The actual interpretation by the hardware of this value is such that one more than the programmed value is used.

Bits 24:16 – NBRP[8:0] Nominal Baud Rate Prescaler

ValueDescription
0x000 - 0x1FFThe value by which the GCLK_CANx is divided for generating the bit time quanta. The bit time is built up from a multiple of this quanta. Valid values for the Baud Rate Prescaler are 0 to 511. The actual interpretation by the hardware of this value is such that one more than the value programmed here is used.

Bits 15:8 – NTSEG1[7:0] Nominal Time segment before sample point

ValueDescription
0x00 - 0x7FValid values are 1 to 255. The actual interpretation by the hardware of this value is such that one more than the programmed value is used. NTSEG1 is the sum of PROPAGATION TIME SEGMENT (PROP_SEG) and PHASE BUFFER SEGMENT1 (PHASE_SEG1).

Bits 6:0 – NTSEG2[6:0] Time segment after sample point

ValueDescription
0x00 - 0x7FValid values are 0 to 127. The actual interpretation by the hardware of this value is such that one more than the programmed value is used. NTSEG2 is PHASE BUFFER SEGMENT2 (PHASE_SEG2).