Boot Assist Module (BAM) RM0046
830/936 Doc ID 16912 Rev 5
Worked examples showing FlexCAN Autobaud rate:
Example 198 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 *(Presdiv+1) * (SYNCSEG + 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 449. PRESDIV + 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
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