38.8.8 Nominal Bit Timing and Prescaler
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
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_CAN periods. tq = (NBRP + 1) mtq.
NTSEG1 is the sum of Prop_Seg and Phase_Seg1. NTSEG2 is Phase_Seg2.
Therefore the length of the bit time is (programmed values) [NTSEG1 + NTSEG2 + 3] tq or (functional values) [Sync_Seg + Prop_Seg + Phase_Seg1 + Phase_Seg2] tq.
The Information Processing Time (IPT) is zero, meaning the data for the next bit is available at the first clock edge after the sample point.
Note: With a CAN clock (GCLK_CAN) of 8MHz, the reset value 0x06000A03 configures the CAN
for a bit rate of 500 kBits/s.
| Name: | NBTP |
| Offset: | 0x1C |
| Reset: | 0x00000A33 |
| Property: | Write-restricted |
| Bit | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | |
| NSJW[6:0] | NBRP[8] | ||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | |
| Bit | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | |
| NBRP[7:0] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| NTSEG1[7:0] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| NTSEG2[6:0] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | ||
| Reset | 0 | 0 | 0 | 0 | 0 | 1 | 1 | ||
Bits 31:25 – NSJW[6:0] Nominal (Re)Syncronization Jump Width
| Value | Description |
|---|---|
| 0x00 - 0x7F | Valid 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
| Value | Description |
|---|---|
| 0x000 - 0x1FF | The value by which the oscillator frequency 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
| Value | Description |
|---|---|
| 0x00 - 0x7F | Valid 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 Prop_Seg and Phase_Seg1. |
Bits 6:0 – NTSEG2[6:0] Time segment after sample point
| Value | Description |
|---|---|
| 0x00 - 0x7F | Valid 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_Seg2. |