AN2320 Freescale Semiconductor / Motorola, AN2320 Datasheet - Page 17

• Manufacturer Part Number: AN2320
• Description: Interfacing the MCF5272 to a Standalone CAN Controller
• Manufacturer: Freescale Semiconductor / Motorola

82C900 Initialisation
The bit timing register controls the data transfer rate on the CAN bus. The bit field descriptions are given
below and are followed by an explanation on how the values in these fields define the baud rate.
CAN bit time is divided into different segments (according to ISO-DIS 11898 standard) and each segment
is a multiple of a time quantum. The segments are shown below. The synchronisation segment (Tsync)
allows phase synchronisation between receiver and transmitter; the propagation time segment (Tprop)
allows for physical propagation delay in the transceiver circuit; the buffer segments (Tbuff1 and Tbuff2)
provide a delay before and after the data sample point to compensate for the phase difference between the
receiver and transmitter detected during synchronisation.
17
15
DIV8
15
14–12
11–8
15–8
Bits
7–6
5–0
Bits
15
7
6
5
4
3
2
1
0
Table 1. Node A/B Control Registers (ACR/BCR)—Lower 16-bits Field Descriptions
Table 2. Node A/B Control Registers (ACR/BCR)—Lower 16-bits Field Descriptions
14
TSEG2 Time segment after sample point.
TSEG1 Time segment before sample point.
LECIE Last error code interrupt enable.
Name
Name
DIV8 Baud rate prescaler clock source (CAN clock or CAN clock/8)
CCE Bit timing register and error counter access enable
SJW
BRP
INIT Connect or disconnect CAN node from bus.
EIE
SIE
TSEG2
CA
—
—
—
Figure 7. Node A/B Control Registers (ACR/BCR)—Lower 16-bits
Reserved
Node used for CAN communication over the bus or as a CAN analyser to monitor bus
activity
Reserved
Error interrupt enable.
Status change interrupt enable.
Reserved
0
Resynchronisation jump width
Baud rate prescaler.
Interfacing the MCF5272 to a Standalone CAN Controller
Figure 8. Node A/B Bit Timing Registers (ABTR, BBTR)
12 11
Freescale Semiconductor, Inc.
For More Information On This Product,
TSEG1
8
8 7
Go to: www.freescale.com
CA
7
SJW
CCE
6
6 5
Description
Description
5
0
LECIE
4
EIE
3
BRP
SIE
2
0
1
MOTOROLA
INIT
0
0