MEGA128CAN Datasheet, PDF (252/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

• Bit 3:1 – PRS2:0: Propagation Time Segment
This part of the bit time is used to compensate for the physical delay times within the
network. It is twice the sum of the signal propagation time on the bus line, the input com-
parator delay and the output driver delay.
Tprs = Tscl x (PRS [2:0] + 1)
CAN Bit Timing Register 3 -
CANBT3
• Bit 0 – Reserved Bit
This bit is reserved for future use. For compatibility with future devices, this must be writ-
ten to zero when CANBT2 is written.
Bit
Read/Write
Initial Value
7
6
5
4
3
2
1
0
-
PHS22 PHS21 PHS20 PHS12 PHS11 PHS10 SMP CANBT3
-
R/W
R/W
R/W
R/W
R/W
R/W
R/W
-
0
0
0
0
0
0
0
• Bit 7– Reserved Bit
This bit is reserved for future use. For compatibility with future devices, this must be writ-
ten to zero when CANBT3 is written.
• Bit 6:4 – PHS22:0: Phase Segment 2
This phase is used to compensate for phase edge errors. This segment may be short-
ened by the re-synchronization jump width. PHS2[2..0] shall be ≥1 and ≤PHS1[2..0] (c.f.
Section “CAN Bit Timing” and Section “Baud Rate”).
Tphs2 = Tscl x (PHS2 [2:0] + 1)
• Bit 3:1 – PHS12:0: Phase Segment 1
This phase is used to compensate for phase edge errors. This segment may be length-
ened by the re-synchronization jump width.
Tphs1 = Tscl x (PHS1 [2:0] + 1)
• Bit 0 – SMP: Sample Point(s)
– 0 - once, at the sample point.
– 1 - three times, the threefold sampling of the bus is the sample point and twice
over a distance of a 1/2 period of the Tscl. The result corresponds to the
majority decision of the three values.
CAN Timer Control Register -
CANTCON
Bit
Read/Write
Initial Value
7
TPRSC7
R/W
0
6
TPRSC6
R/W
0
5
TPRSC5
R/W
0
4
TPRSC4
R/W
0
3
TPRSC3
R/W
0
2
TPRSC2
R/W
0
1
TRPSC1
R/W
0
0
TPRSC0
R/W
0
CANTCON
• Bit 7:0 – TPRSC7:0: CAN Timer Prescaler
Prescaler for the CAN timer upper counter range 0 to 255. It provides the clock to the
CAN timer if the CAN controller is enabled.
CLK_CANTIM = CLK_IO x 8 x (CANTCON [7:0] + 1)
252 AT90CAN128
4250E–CAN–12/04