Chapter 33 Boot Assist Module (BAM)
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
841
Worked examples showing FlexCAN Autobaud rate:
Example 33-5. 8 MHz crystal
Consider case where using an 8 MHz crystal, user attempts to send 1 MB (max permissible baud
rate) FlexCAN message.
— Time base, clocking at crystal frequency, would measure:
— 1MB = 8 clocks/bit => 29 * 8 = 232 clocks
— To calculate PRESDIV = 232/725 =>PRESDIV = 0
— To calculate time quanta requirement:
— Time base result = 29 *(1) * (S TSEG1 + TSEG2)
— 232 = 29 * 1 * (1 + TSEG1 + TSEG2)
— 1 + TSEG1 + TSEG2 = 8.
— From the lookup table, CANA_CR = 0x004A_2001.
— This give a baud rate of X. This give 0% error.
Table 33-16. P 1 > 1 (YY = PRESDIV)
Desired number of time quanta
Register contents for CANA_CR
8
0xYY49_2002
9
0xYY49_2003
10
0xYY49_2004
11
0xYY49_2005
12
0xYY49_2006
13
0xYY49_2007
14
0xYY52_2007
15
0xYY52_2008
16
0xYY5B_2008
17
0xYY5B_2009
18
0xYY64_2009
19
0xYY64_200A
20
0xYY6D_200A
21
0xYY6D_200B
22
0xYY76_200B
23
0xYY76_200C
24
0xYY7F_200C
25
0xYY7F_200D