tmp89fm42 TOSHIBA Semiconductor CORPORATION, tmp89fm42 Datasheet - Page 233

• Manufacturer Part Number: tmp89fm42
• Description: 8 Bit Microcontroller
• Manufacturer: TOSHIBA Semiconductor CORPORATION

RA001
PE
0
0
1
1
RTSEL
000
001
010
011
100
16.8.1.2 Calculation of set values of UART0CR2<RTSEL> and UART0DR
STBT
Figure 16-4 Fine Adjustment of Baud Rate Clock Using UART0CR2<RTSEL>
0
1
0
1
Figure 16-5 UART0DR Calculation Method (When BRG Is Set to fcgck)
lation formula shown in Figure 16-5. For example, to generate a basic baud rate of 38400 [baud] with
fcgck=4 [MHz], calculate the set value of UART0DR for each setting of UART0CR2<RTSEL> and com-
pensate the calculated value to a positive number to obtain the generated baud rate as shown in Figure 16-
6. Basically, select the set value of UART0CR2<RTSEL> that has the smallest baud rate error from
among the generated baud rates. In Figure 16-6, the setting of UART0CR2<RTSEL>="0y010" has the
smallest error among the calculated baud rates, and thus the generated baud rate is 38095 [baud] (0.79%)
against the basic baud rate of 38400 [baud].
Start
Start
Start
Start
The set value of UART0DR for an operating frequency and baud rate can be calculated using the calcu-
Note: The error from the basic baud rate should be accurate to within r3%. Even if the error is within r3%, the
16
16
15
15
17
1
communication may fail due to factors such as frequency errors of external controllers (for example, a
personal computer) and oscillators and the load capacity of the communication pin.
Bit 0
Bit 0
Bit 0
Bit 0
16
17
15
16
17
2
Bit 1
Bit 1
Bit 1
Bit 1
16
16
15
15
17
3
Bit 2
Bit 2
Bit 2
Bit 2
16
17
15
16
17
4
RTSEL
000
001
010
011
100
Bit 3
Bit 3
Bit 3
Bit 3
16
16
15
15
17
5
Number of RT clocks
Transfer frame
Bit 4
Bit 4
Bit 4
Bit 4
UARTDR =
UARTDR =
UARTDR =
UARTDR =
UARTDR =
16
17
15
16
17
6
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UARTDR set value
Bit 5
Bit 5
Bit 5
Bit 5
16
16
15
15
17
7
16.5 A [baud]
15.5 A [baud]
16 A [baud]
15 A [baud]
17 A [baud]
Bit 6
Bit 6
Bit 6
Bit 6
fcgck [Hz]
fcgck [Hz]
fcgck [Hz]
fcgck [Hz]
fcgck [Hz]
16
17
15
16
17
8
Bit 7
Bit 7
Bit 7 Parity
Bit 7
16
16
15
15
17
9
Stop 1
Stop 1 Stop 2
Parity
10
16
17
15
16
17
1
1
1
1
1
Stop 1
Stop 1 Stop 2
11
16
16
15
15
17
12
16
17
15
16
17
*When BRG is set to fcgck
16.5 (UARTDR+1)
15.5 (UARTDR+1)
16 (UARTDR+1)
15 (UARTDR+1)
17 (UARTDR+1)
Generated baud rate
fcgck
fcgck
fcgck
fcgck
fcgck
TMP89FM42
[baud]
[baud]
[baud]
[baud]
[baud]