ST SPC560P34 - Figure 490. Baud Rate Deviation between Host and SPC560 P40;34

RM0046 Boot Assist Module (BAM)
Doc ID 16912 Rev 5 825/936
Higher baud rates high may be used, but the user will be required to ensure they fall within
an acceptable error range. This is illustrated in Figure 490, which shows the effect of
quantization error on the baud rate selection.
Figure 490. Baud rate deviation between host and SPC560P40/34
Example 18Baud rate calculation for 250 kBaud signal
Considering reception of a 250kBaud signal from the host and SPC560P40/34 operating
with a 4 MHz oscillator. Over 9 bits the time base will measure: (9 × 4e6)/250e3 =
144 cycles.
Thus, LINIBB is set to 144/144 = 1. This results in a baud rate of exactly 250 kBd.
However, a slower 225 kBd signal operating with 4 MHz XTAL would again result in
LINIBB = 1, but this time with an 11.1% deviation.
16
51.2 Kbit/s
(SBR = 20)
120 bit/s
(SBR = 8192)
20
64.0 Kbit/s
(SBR = 20)
150 bit/s
(SBR = 8192)
Table 444. Maximum and minimum recommended baud rates (continued)
f
sys
=f
xtal
(MHz)
Max baud rate for guaranteed
<2.5% deviation
Min baud rate for guaranteed
<2.5% deviation
0 10000
Host baud rate
20000 30000 40000 50000
10.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
Baud rate deviation between host and device