CC1010-RTR1 datasheet(69/152 Pages) TI

69 / 152 page

CC1010

SWRS047

Page 69 of 152

The clock output is high when the serial

port is idle. In reception, data is shifted in

on the rising edge of the clock. In

transmission, each new bit is set on the

falling edge of the clock.

T1M/TH1

Baudrate

(kBaud)

Fxosc =

3.6864

MHz

Fxosc =

7.3728

MHz

Fxosc =

11.0592

MHz

Fxosc =

14.7456

MHz

Fxosc =

18.4320

MHz

Fxosc =

22.1184

MHz

57.6

1/255

1/254

0/255

1/252

1/251

1/250

19.2

1/253

1/250

0/253

0/252

1/241

1/238

9.6

1/250

1/244

0/250

0/248

1/226

1/220

4.8

1/244

1/232

0/244

0/240

1/196

1/184

2.4

1/232

1/208

0/232

0/224

1/136

1/112

1.2

1/208

1/160

0/208

0/192

1/16

0/160

Table 23. Baud rate examples (SMODx=1)

16.7.2

MODE1

Mode 1 provides standard asynchronous

full duplex communication, using a total of

10 bits: 1 start bit, 8 data bits and 1 stop

bit. For receive operations, the stop bit is

stored

SCON0.RB8_0

(or

SCON1.RB8_1). Data bits are received

and transmitted with their LSB first.

The baud rate for mode 1 is a function of

timer 1 overflow. Each time the timer

increments from its maximum count

(0xFF), a clock pulse is sent to the baud

rate circuit, to be further divided by 16 or

set

PCON.SMOD0

EICON.SMOD1 to give the baud rate:

overflow

Timer

Rate

Baud

⋅

SMODx

As can be seen from the equation above,

both

serial

ports

are

use

simultaneously, the baud rate is equal or

different by a factor 2.

It is common to use Timer 1 in Mode 2 (8-

bit counter with auto-reload) for baud rate

generation, although any timer mode can

be used. The Timer 1 reload value is

stored in the TH1 register, which makes

the complete baudrate using mode 2:

)

256

(

)

(

TH1

T1M

SMODx

−

⋅

−

⋅

system

Rate

Baud

T1M in the above equation is in register

CKCON (see page 55), and controls the

initial division in Timer 1 between 4 and

12.

Some example baud rates and reload

values are shown in Table 23. The setting

for other baud rates and oscillator

frequencies can be determined by using

the above equation.

To transmit data in mode 1, write data to

SBUF0 / SBUF1. Transmission is then

performed on TXD0 / TXD1 in the following

order: start bit, 8 data bits (LSB first) and

then the stop bit.

Reception begins on the falling edge of a

start bit received on RXD0 / RXD1, if

reception is enabled in SCON0.REN_0 /

SCON1.REN_1. The data input is sampled

16 times per baud for any baud rate. Each

bit decision is performed as a majority

decision between 3 successive samples in

the middle of each baud. If the majority

decision is not equal to zero for the start

bit, the serial port will stop reception and

wait for a new start bit.

When the majority decision is made for the

stop-bit, the following conditions must be

met:

•

RI_0 / RI_1 is 0

•

If SM2_0 / SM2_1 is set, the state of

the stop bit must be one

If these conditions are met, the received

data is buffered in SBUF0 / SBUF1, the

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