3-3 how to use the baud rate timer – Panasonic MN101C00 User Manual

Page 119

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5-3-3 How to Use the Baud Rate Timer

Refer to the following when using the baud rate timer to set the UART transfer

speed.

(1) Specifying the timer clock source

The clock source is specified by the TM3CKS3 to 1 flags of the timer 3

mode register (TM3MD).

(2) Setting the compare register

The compare register value is set in the timer 3 compare register (TM3OC).

This set value is computed according to the following formula:

overflow period = (compare register set value + 1)

×

timer clock period

baud rate = 1/(overflow period

Ч

2

Ч

8)

↑

SC0MD1(SC0CKM)

compare register set value = timer clock frequency/(baud rate

Ч

2

Ч

8) – 1

Table 5-3-1 UART Transfer Rate

Example:

The timer 3 clock source is fs/4 (fosc = 8MHz) and a baud rate of 300 bps is

desired.

Since fs=fosc/2,

compare register set value = (8

Ч

10

6

/2/4)/(300

Ч

2

Ч

8) – 1

=207

= X'CF'

Chapter 5 Serial Functions

105

Half-duplex UART Serial Interface

4.0

fosc

(MHz)

Transfer Speed
(bps)

fosc

fs/4

fs/16

—

104

—

—

Set

Value

Calculated

Value

Set

Value

Calculated

Value

Set

Value

Calculated

Value

Set

Value

Calculated

Value

Set

Value

Calculated

Value

Set

Value

Calculated

Value

300

—

208

—

—

1202

—

—

104

—

—

2403

—

—

52

—

—

4807

—

—

26

—

—

9615

—

—

13

—

—

19230

—

—

—

109

—

—

300

—

218

—

—

1201

—

—

109

—

—

2402

—

—

55

—

—

4761

—

—

27

—

—

9699

—

—

—

—

—

—

—

—

—

208

—

—

300

—

—

52

—

—

1201

—

208

—

—

2404

—

—

104

—

—

4807

—

—

52

—

—

9615

—

—

26

—

—

19230

—

—

—

218

—

—

300

—

—

55

—

—

1190

—

218

—

—

2403

—

—

109

—

—

4805

—

—

55

—

—

9523

—

—

27

—

—

19398

—

—

—

—

78

—

—

300

—

78

—

—

1202

—

—

39

—

—

2403

—

156

—

—

4808

—

—

78

—

—

9615

—

—

39

—

—

19230

—

—

—

—

104

—

—

300

—

104

—

—

1202

—

—

52

—

—

2404

—

208

—

—

4808

—

—

104

—

—

9615

—

—

52

—

—

19230

—

—

—

—

109

—

—

300

—

109

—

—

1201

—

—

55

—

—

2381

—

218

—

—

4805

—

—

109

—

—

9610

—

—

55

—

—

19045

—

—

—

—

130

—

—

300

—

130

—

—

1202

—

—

65

—

—

2404

—

—

33

—

—

4735

—

130

—

—

9615

—

—

65

—

—

19231

—

—

fosc

fs/4

fs/16

fosc

fs/4

fs/16

fosc

fs/4

fs/16

fosc

fs/4

fs/16

fosc

fs/4

fs/16

fosc

fs/4

fs/16

fosc

fs/4

fs/16

300

1200

2400

4800

9600

19200

4.19

8.0

8.38

12.0

16.0

16.76

20.0

Set the values from this table

(minus 1) in the compare

register.

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