TMP93CS44 datasheet(135/224 Pages) TOSHIBA

135 / 224 page

TMP93CS44/S45

2004-02-10

93CS44-133

The clock selected among fFPH clock, fc/16 clock, and fs clock is divided by 4 and

input to this prescaler.

This is selected by prescaler clock selection register SYSCR0<PRCK1:0>.

Resetting sets <PRCK1:0> to “00” and selects the fFPH clock input divided by 4.

The baud rate generator selects between 4 clock inputs:

φT0, φT2, φT8, and φT32

among the prescaler outputs.

The prescaler can be run or stopped by the timer operation control register

TRUN<PRRUN>. Counting starts when <PRRUN> is set to “1”, while the prescaler is

cleared to zero and stops operation when <PRRUN> is set to “0”.

When the IDLE1 mode (operates only oscillator) is used, set TRUN<PRRUN> to “0”

to reduce the power consumption of this prescaler before “HALT” instruction is

executed.

2. Baud rate generator

Baud rate generator comprises 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 1 to 16 values to determine the transfer rate.

How to calculate a transfer rate when the baud rate generator is used is explained

below.

•

UART mode

Baud rate

÷ 16

•

I/O interface mode

Baud rate

÷ 2

Accordingly, when source clock fc is 12.288 MHz, input clock is

φT2 (fc/16), and

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

* Clock condition

System clock:

High frequency (fs)

Clock gear:

1 (fc)

Prescaler clock: fFPH

Baud rate

÷ 16

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

The maximum baud rate of this baud rate generator is 307.2 kbps.

Table 3.9.2 shows an example of the transfer rate in UART mode.

Also with 8-bit timer 2, the serial channel can get a transfer rate. Table 3.9.3 shows

an example of baud rate using timer 2.

Input clock of baud rate generator

Frequency divisor of baud rate generator

Input clock of baud rate generator

Frequency divisor of baud rate generator

fc/16

TMP93CS44 Datasheet(PDF) 135 Page - Toshiba Semiconductor

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