tmp89fm42 TOSHIBA Semiconductor CORPORATION, tmp89fm42 Datasheet - Page 232

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

16.8 Transfer Baud Rate
16. Asynchronous Serial Interface (UART)
RA001
16.8.1 Transfer baud rate calculation method
16.8.1.1 Bit width adjustment using UART0CR2<RTSEL>
Note 1: The overall error from the basic baud rate must be within r3%. Even if the overall error is within r3%, the commu-
nication may fail due to factors such as frequency errors in external controllers (for example, a personal computer)
and oscillators and the load capacity of the communication pin.
The number of RT clocks per bit can be changed in a range of 15 to 17 clocks by changing
UART0CR2<RTSEL>. The RT clock is the transfer base clock, which is the pulses obtained by counting
the clock selected at UART0CR1<BRG> the number of times of (UART0DR set value) + 1. Especially,
when UART0CR2<RTSEL> is set to "0y001" or "0y011", two types of RT clocks alternate at each bit, so
that the pseudo baud rates of RT u 15.5 clocks and RT u 16.5 clocks can be generated. The number of RT
clocks per bit of transfer frame is shown in Figure 16-4.
"0x19", the baud rate calculated using the formula in Figure 16-4 is expressed as:
The bit width of transmitted/received data can be finely adjusted by changing UART0CR2<RTSEL>.
For example, when fcgck is 4 [MHz], UART0CR2<RTSEL> is set to "0y000" and UART0DR is set to
fcgck / (16 u (UART0DR + 1) = 9615 [baud]
These settings generate a baud rate close to 9600 [baud] (+0.16%).
Table 16-7 Set Values of UART0DR and UART0CR2<RTSEL> for Transfer
Basic baud
[baud]
rate
300
150
134
110
75
Baud Rates (fs=32.768 kHz, UART0CR2<RXDNC>=0y00)
UART0DR
UART0DR
UART0DR
UART0DR
UART0DR
Register
RTSEL
RTSEL
RTSEL
RTSEL
RTSEL
Error
Error
Error
Error
Error
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Operating frequency
32.768 kHz
(+0.67%)
(+0.67%)
(+0.30%)
(+0.44%)
(-1.20%)
0y011
0y011
0y001
0y001
0y010
0x0D
0x0E
0x1C
0x06
0x11
TMP89FM42