Rainbow Electronics AT91CAP9S250A - Manual (Page 720)

720
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
39.8.6 CAN Baudrate Register
Name: CAN_BR
Access Type: Read/Write
Any modification on one of the fields of the CANBR register must be done while CAN module is disabled.
To compute the different Bit Timings, please refer to the Section 39.6.4.1 ”CAN Bit Timing Configuration” on page 688 .
• PHASE2: Phase 2 segment
This phase is used to compensate the edge phase error.
Warning: PHASE2 value must be different from 0.
• PHASE1: Phase 1 segment
This phase is used to compensate for edge phase error.
• PROPAG: Programming time segment
This part of the bit time is used to compensate for the physical delay times within the network.
• SJW: Re-synchronization jump width
To compensate for phase shifts between clock oscillators of different controllers on bus. The controller must re-synchronize
on any relevant signal edge of the current transmission. The synchronization jump width defines the maximum of clock
cycles a bit period may be shortened or lengthened by re-synchronization.
• BRP: Baudrate Prescaler.
This field allows user to program the period of the CAN system clock to determine the individual bit timing.
The BRP field must be within the range [1, 0x7F], i.e., BRP = 0 is not authorized.
• SMP: Sampling Mode
0 = The incoming bit stream is sampled once at sample point.
1 = The incoming bit stream is sampled three times with a period of a MCK clock period, centered on sample point.
SMP Sampling Mode is automatically disabled if BRP = 0.
39.8.7 CAN Timer Register
Name: CAN_TIM
31 30 29 28 27 26 25 24
– – – – – – – SMP
23 22 21 20 19 18 17 16
– BRP
15 14 13 12 11 10 9 8
– – SJW – PROPAG
7 6 5 4 3 2 1 0
– PHASE1 – PHASE2
t
PHS2
t
CSC
PHASE2 1 +
( ) ×
=
t
PHS1
t
CSC
PHASE1 1 +
( ) ×
=
t
PRS
t
CSC
PROPAG 1 +
( ) ×
=
t
SJW
t
CSC
SJW 1 +
( ) ×
=
t
CSC
BRP 1 +
( )
MCK
⁄
=