TMP93CS41 datasheet(183/248 Pages) TOSHIBA

183 / 248 page

TMP93CS40/TMP93CS41

2004-02-10

93CS40-181

2. Baud rate generator

The baud rate generator is a circuit that generates transmission and receiving clocks

to determine the transfer rate of the serial channel.

The input clock to the baud rate generator,

φT0, φT2, φT8, or φT32, is generated by

the 9-bit prescaler which is shared by the timers. One of these input clocks is selected

by the baud rate generator control register BR0CR<BR0CK1:0>.

The baud rate generator includes a 4-bit frequency divider, which divides frequency

by from 2 to 16 to determine the transfer rate.

The method for calculating a transfer rate when the baud rate generator is used is

explained below.

•

UART mode

Input clock for baud rate generator

Baud rate =

Frequency divisor for baud rate generator

÷ 16

•

I/O interface mode

Input clock for baud rate generator

Baud rate =

Frequency divisor for baud rate generator

÷ 2

For example, when the source clock (fc) is 12.288 MHz, the input clock is

φT2 (fc/16),

and the frequency divisor is 5, the transfer rate in UART mode is as follows:

Clock configuration

System clock:

High frequency (fc)

Clock gear:

1 (fc)

Prescaler clock: fFPH

fc/16

Baud rate

÷16

= 12.288 × 106 ÷ 16 ÷ 5 ÷ 16 = 9600 (bps)

Table 3.11.2 shows an example of the transfer rate in UART mode.

Also, using the 8-bit timer 0, the serial channel can generate a transfer rate. Table

3.11.3 shows examples of baud rate settings using timer 0.

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