UPD784938 Datasheet, PDF (454/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 18 ASYNCHRONOUS SERIAL INTERFACE/3-WIRE SERIAL I/O
18.4.4 Baud rate setting in asynchronous serial interface mode
There are two methods of setting the baud rate, as shown in Table 18-3.
This table shows the range of baud rates that can be generated, the baud rate calculation expression and selection
method for each case.
Table 18-3. Baud Rate Setting Methods
Baud Rate Clock Source
Selection Method
Baud rate generator Internal system clock SCK in ASIM = 1
ASCK input
SCK in ASIM = 0
Baud Rate Calculation
Expression
fXX
(k + 16) • 2ⁿ⁺²
fASCK
2ⁿ⁺⁶
Baud Rate Range
fXX _to fXX
245,760 64
fASCK
to ^fASCKNote
131,072
64
Note Including fASCK input range: (0 to fXX/256)
Remarks fXX: Oscillator frequency or external clock input frequency
k: Value set in bits MDL3 to MDL0 of BRGC (k = 0 to 14; see Figure 18-15)
n: Value set in bits TPS3 to TPS0 of BRGC (n = 0 to 11; see Figure 18-15)
fASCK: ASCK input clock frequency (0 to fXX/4)
(1) Examples of settings when baud rate generator is used
Examples of baud rate generator control register (BRGC) settings when the baud rate generator is used are shown
below.
When the baud rate generator is used, the SCK bit of the asynchronous serial interface mode register (ASIM) should
be set (to 1).
Table 18-4. Examples of BRGC Settings when Baud Rate Generator is Used
Oscillator Frequency (fXX)
or External Clock (fX)
12.0 MHz
Baud Rate
[bps]
BRGC Value
Error
(%)
75
A4H
2.34
110
9BH
1.36
150
94H
2.34
300
84H
2.34
600
74H
2.34
1,200
64H
2.34
2,400
54H
2.34
4,800
44H
2.34
9,600
34H
2.34
19,200
24H
2.34
31,250
19H
0.00
38,400
14H
2.34
76,800
04H
2.34
11.0592 MHz
BRGC Value
A2H
99H
92H
82H
72H
62H
52H
42H
32H
22H
16H
12H
02H
Error
(%)
0.00
1.82
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.54
0.00
0.00
454
Preliminary User’s Manual U13987EJ1V0UM00