Datasheet

Registers
MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor 133
Use the following formula to calculate the ESCI baud rate:
where:
SCI clock source = bus clock or BUSCLKX4 (selected by ESCIBDSRC in the configuration register)
BPD = Baud rate register prescaler divisor
BD = Baud rate divisor
PD = Prescaler divisor
PDFA = Prescaler divisor fine adjust
Table 13-10 shows the ESCI baud rates that can be generated with a 4.9152-MHz bus frequency.
0 1 1 1 1 15/32 = 0.46875
10000 16/32 = 0.5
1 0 0 0 1 17/32 = 0.53125
1 0 0 1 0 18/32 = 0.5625
1 0 0 1 1 19/32 = 0.59375
1 0 1 0 0 20/32 = 0.625
1 0 1 0 1 21/32 = 0.65625
1 0 1 1 0 22/32 = 0.6875
1 0 1 1 1 23/32 = 0.71875
1 1 0 0 0 24/32 = 0.75
1 1 0 0 1 25/32 = 0.78125
1 1 0 1 0 26/32 = 0.8125
1 1 0 1 1 27/32 = 0.84375
1 1 1 0 0 28/32 = 0.875
1 1 1 0 1 29/32 = 0.90625
1 1 1 1 0 30/32 = 0.9375
1 1 1 1 1 31/32 = 0.96875
Table 13-9. ESCI Prescaler Divisor Fine Adjust (Continued)
PSSB[4:3:2:1:0] Prescaler Divisor Fine Adjust (PDFA)
Frequency of the SCI clock source
64 x BPD x BD x (PD + PDFA)
Baud rate =