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XC161 Derivatives
Peripheral Units (Vol. 2 of 2)
IIC-Bus Module
User’s Manual
20-15
V2.2, 2004-01
IIC_X, V2.0
20.3.5
Baud Rate Generation
In order to give the user high flexibility in selection of CPU frequency and IIC-Bus
baudrate without constraints to baudrate accuracy, a flexible baudrate generator has
been implemented. It uses two different modes and an additional pre-divider. Low
baudrates may be configured at high precision in mode 0, which is compatible with
previous implementations of the IIC-Bus module. High baudrates may be configured
precisely in mode 1.
Figure 20-4
IIC-Bus Module Baudrate Generator
Reciprocal Divider Mode (BRPMOD = 0)
The resulting baudrate is:
(20.1)
Table 20-1
IIC-Bus Baudrate Examples for Mode 0
BRPMOD = 0
BRP @ 100 kbit/s
BRP @ 400 kbit/s
f
IIC
[MHz]
PREDIV = 00
B
PREDIV = 01
B
PREDIV = 00
B
PREDIV = 01
B
40
63
H
0B
H
18
H
02
H
24
3B
H
06
H
0E
H
–
20
31
H
05
H
0B
H
–
16
27
H
04
H
09
H
–
10
18
H
02
H
05
H
–
8
13
H
01
H
04
H
–
MCA05466
Prescale Value BRP
Baudrate Generator
Circuitry
B
IIC
f
IIC
PREDIV
BRPMOD
MUX
64:1
8:1
B0
IIC
f
IIC
4
2
<PREDIV>
3
×
<BRP>
1
+
(
)
×
×
-------------------------------------------------------------------------------
=
BRP
f
IIC
4
2
<PREDIV>
3
×
B0
IIC
×
×
-----------------------------------------------------------
1
–
=