Renesas R8C/11 Series Installation and operating instructions

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 1 of 21

PPLICATION NOTE

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator

Using a Commercial Frequency

1. Abstract

This application note describes a program that adjusts the oscillation frequency of the high-speed on-chip

oscillator using a commercial frequency (50/60 Hz).

2. Introduction

The explanation of this issue is applied to the following condition:

Microcomputer : R8C/11, R8C/13 Group

RAM size, ROM size :1 Kbytes, 16 Kbytes

This program can also be used when operating other microcomputers within the R8C/Tiny, provided they

have the same SFR (Special Function Registers) as the R8C/11 microcomputers. However, some functions

may have been modified.

Refer to the Hardware Manual for details. Use functions covered in thisApplication Note only after careful

evaluation.

3. Contents

3.1 Outline of the High-speed On-chip Oscillator

The R8C/11 group of microcomputers incorporate approximately an 8 MHz high-speed on-chip oscillator. The

operating oscillation frequency of the on-chip oscillator tends to fluctuate due to external factors such as the

operating temperature and power supply voltage. The oscillation frequency can be adjusted by setting up the

HR1 register appropriately.

The relationship between the set value of the HR1 register and the oscillation period of the high-speed

on-chip oscillator is shown below. However, because the amount of delay in each bit is not even, be sure to

change each bit to adjust. Also make sure bit 7 is set to “0”.

b5 b4 b3 b2 b1 b0

Oscillation period of the high-speed on-chip oscillator=td(HRoffset)+(b6+ 2 + 4 + 8 + 16 + 32 + 64 ) ×td(HR)

This application note explains how to adjust the oscillation frequency of the high-speed on-chip oscillator

using a commercial frequency (50/60 Hz).

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 2 of 21

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

3.2 Outline of the Program

The following shows how to adjust the oscillation frequency of the high-speed on-chip oscillator using a

commercial frequency.

Measure the commercial frequency with timer C that uses the high-speed on-chip oscillator as its count

source. Adjust the high-speed on-chip oscillator to 8 MHz by adjusting the HR1 register in such a way that

the measured value and the logical value match.

The logical value can be obtained by the equation given below.

Expected frequency of the high-speed on-chip oscillator

Logical measurement value of timer C = Commercial frequency ×Divide-by-N value of the high-speed on-chip oscillator

Figure 1. Measuring the Commercial Frequency

The adjustment rate of the HR1 register (difference in the oscillation period when the HR1 register is set to

00h and when it is set to 01h) is 1 ns. Table 1 shows the relationship between the set value of the HR1

frequency can be adjusted to 8 MHz.

Table 1. HR1 Set Value and Timer C Measured Value

Oscillation of the high-speed

on-chip oscillator Timer C measured value (when

measuring 60 Hz)

HR1 set

value Period Frequency Not divided Divided by 8

n-2 123ns 8.13MHz 135501 16938

n-1 124ns 8.06MHz 134409 16801

n 125ns 8.00MHz 133333 16667

n+1 126ns 7.94MHz 132275 16534

n+2 127ns 7.87MHz 131234 16404

In this application note, timer C is used as divided-by-8, and the measured value is divided by 100 before

being compared with the logical value (166). When the measured value and the logical value match, the

oscillation frequency is in the range of 7.97 MHz (timer C measured value = 16600) to 8.02 MHz (timer C

measured value = 16699).

“L”

50Hz or 60Hz

Measured by timer C

Logical measurement value when adjusting the high-speed on-chip oscillator to 8 MHz

Logical valueCommercial

frequency Not divided Divided by 8

50Hz 160000 20000

60Hz 133333 16667

Commercial

frequency

(after converted to

square wave)

“H”

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 3 of 21

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

Adjust the high-speed on-chip oscillator during initial operating time and save the set value in the flash ROM.

Make sure the address to which it is saved does not match that of a block where the program is located.A

sample program memory map is shown in Figure 2.

From the next time on (after the HR1 adjustment value is saved), read the initial value of the HR1 register

from the data flash and set it in the HR1 register. Thereafter, fine-adjust the oscillation frequency each time a

rising edge of the commercial frequency is detected.

Figure 2. Sample Program Memory Map

3.3 Pins Used

Table 2. List of Pins Used and Their Functions

Pin name I/O Fuction

P33/INT

______3/TCIN Input Commercial frequency (square wave) input

Figure 3. Commercial Frequency Input

R8C/11

P33/INT

______3/TCIN

Commercial frequency converter circuit

(sine wave -> square wave)

Note: Power supply voltage is Vcc.

0000h

0400h

041Fh

0420h

0620h

C000h

D000h

D7DBh

E000h

FEDBh

FEDCh

FFDCh

FFFFh

Data area

Stack Area

Program area (Note 1)

HR1 adjustment value (Note 1)

Relocatable vector

Fixed vector

Block 1

Block 0

Note 1: In this application note, the HR1 adjustment value is written using EW1 mode. For this reason,

consideration is taken to ensure that the block where the rewrite program is located and the block into

which the HR1 adjustment value is written will not match.

Commercial powe

supply

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 4 of 21

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

4. Function Table and Flow Chart

4.1 Function Table

Declaring void main(void)

Outline Main

Argument Type MeaningArgument None

Return Value Type Value MeaningReturn Value None

Function Description Initializes the SFR and performs LOOP processing

Declaring void sfr_init(void)

Outline SFR initialize

Argument Type MeaningArgument None

Return Value Type Value MeaningReturn Value None

Function Description Initializes the SFR

Declaring void first_hz_adjut(void)

Outline Initial frequency adjust

Argument Type MeaningArgument None

Return Value Type Value MeaningReturn Value None

Function Description Adjusts the high-speed on-chip oscillator during initial startup time

Declaring void write_ringadjust_data(unsigned char data)

Outline Frequency adjustment value write

Argument Type MeaningArgument unsigned char data Adjustment value

Return Value Type Value MeaningReturn Value None

Function Description Writes the HR1 register adjustment value to the flash ROM

Declaring void flash_open_ew1_mode(void)

Outline EW1 mode enter

Argument Type MeaningArgument None

Return Value Type Value MeaningReturn Value None

Function Description Enables CPU rewrite mode (EW1 mode)

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 5 of 21

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

Declaring void flash_close_ew1_mode(void)

Outline EW1 mode exit

Argument Type MeaningArgument None

Return Value Type Value MeaningReturn Value None

Function Description Disables CPU rewrite mode (EW1 mode)

Declaring int flash_byte_write(unsigned char *address , unsigned char data)

Outline Flash write

Argument Type Meaning

unsigned char *address Write address

Argument

unsigned char data Write data

Return Value Type Value MeaningReturn Value int chk_flash_status() Flash write status

Function Description Writes 1-byte data (data) to the write address (*address)

Declaring int chk_flash_status(void)

Outline Full status check

Argument Type MeaningArgument None

Return Value Type Value MeaningReturn Value int chk_flash_status() Flash rewrite status

Function Description Performs full status check and returns the flash rewrite status (terminated

normally, command sequence error, erase error, or programming error).

Declaring void int3_hz_in(void)

Outline High-speed on-chip oscillator adjust (INT3 interrupt)

Argument Type MeaningArgument None

Return Value Type Value MeaningReturn Value None

Function Description Executes interrupt processing upon detecting a falling edge of the input signal to

the INT

______3/TCIN pin. The high-speed on-chip oscillator is adjusted based on the

measured value of timer C.

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 6 of 21

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

4.2 Flow Chart

4.2.1 Main Function

main()

sfr_init()

SFR initialize

Initial adjustment finished ?

Yes

Set the ports and set the initial value of the HR1

If the adjustment value is saved in the flash ROM (hr1_flash_data !

= 0xFF), it means that the initial adjustment has been completed.

Set clock source for CPU clock

and peripheral function clock to

high-speed on-chip oscillator

first_hz_adjust()

Initial frequency adjust

End

Reset the microcomputer in software after the

initial frequency adjustment has finished.

Set initial adjustment value in HR1

Set tcc0

Count source = f8

Select INT

______3 rising edge

Select INT

______3 interrupt

Set tcc1

No filter

Select capture

Timer C starts

Enable INT

______3 interrupt (level 7)

I flag = 1 (interrupt enabled)

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 7 of 21

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Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

4.2.2 SFR Initialize Function

sfr_init()

Initialize port P3

return

Initialize HR1 register

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 8 of 21

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

4.2.3 Initial Frequency Adjust Function

Yes

first_hz_adjut()

Set tcc0

Count source = f8

Select INT

______3 rising edge

Select INT

______3 interrupt

Set tcc1

No filter

Select capture

Yes

Wait until the first high-going transition of the commercial

frequency input signal occurs.

Clear INT

______3 interrupt request

Clear INT

______3 interrupt request

in_timerc0 = tm0 Save the timer value synchronously with the rising edge of the commercial

frequency input signal.

Clear INT

______3 interrupt request

in_timerc1 = tm0 Save the timer value synchronously with the rising edge of the commercial

frequency input signal.

dat=in_timerc1-in_timerc0 Find the difference with the timer value that was previously saved on the rising edge

of the commercial frequency input signal to measure the period of the commercial

frequency.

in_timerc0 = in_timerc1in_timerc0 = in_timerc1

dat = dat / 100

dat

dat=166

(matches with

logical value)

IR_INT3=0?

f_upflag = 1

f_downflag = 1

dat<166

(high-speed on-chip oscillator slower

than 8 MHz)

dat>166

(high-speed on-chip oscillator

faster than 8 MHz)

f_upflag=1? f_downflag=1?

Frequency adjustment value write

write_ringadjust_data(hr1)

HR1 != 0x00? HR1 < 0x7f?

HR1 = HR1 + 1HR1 = HR1 - 1

Frequency adjustment

value write

write_ringadjust_data(hr1)

Does not match with logical value when

f_downflag and f_upflag = 1. The value

at that time is approximated to 8 MHz.

Yes

return

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 9 of 21

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Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

4.2.4 Frequency Adjustment Value Write Function

4.2.5 EW1 Mode Enter Function

write_ringadjust_data(unsigned char data)

return

[Argument]

data: HR1 adjustment value

Enter the CPU rewrite mode 1 (EW1 mode).

Write the HR1 adjustment value to the flash ROM.

For the address to which to write, specify a block where the program is not

located.

Set the PM03 bit in the PM0 register to “1” (software reset).

Software reset

flash_open_ew1_mode()

EW1 mode enter

flash_byte_write(HR1_FLASH_ROM,data)

Flash write

Exit the CPU rewrite mode 1 (EW1 mode).

flash_close_ew1_mode()

EW1 mode exit

flash_open_ew1_mode()

return

Divide main clock by 8 Before entering the CPU rewrite mode, reduce the CPU clock frequency to 5

MHz or less.

fmr01 = 0

fmr01 = 1

fmr02 = 0

To set the fmr01 bit to “1” (CPU rewrite mode enabled), write “0” and then “1”

in succession.

fmr02 = 1

To set the fmr02 bit to “1” (block 0, 1 rewrite enabled), write “0” and then “1”

in succession.

fmr11 = 0

fmr11 = 1

To set the fmr11 bit to “1” (EW1 mode), write “0” and then “1” in succession.

REJ05B0471-0100Z/Rev.1.00 July 2004 Page 10 of 21

R8C/11, R8C/13 Group

Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency

4.2.6 EW1 Mode Exit Function

4.2.7 Flash Write Function

flash_close_ew1_mode()

return

fmr01 = 0 If the fmr01 bit is set to “0” (CPU rewrite mode disabled), the fmr11 bit is also

set to “0” (EW0 mode).

flash_byte_write(unsigned char *address, unsigned char data) [Argument]

*address: Address to which the HR1 adjustment value is written

data: Write data (HR1 adjustment value)

Yes

i = 0

flash_address = address

*flash_address = 0x50

s a result of full status check, if an error occur

ed, issue a

status clear command.

i < 4?

*flash_address = 0x40

*flash_address = data

Issue a program command.

Write 0x40 in the first bus cycle and data in

the second bus cycle.

No error?

fmr00 = 0? Wait until the flash write operation finishes.

chk_flash_status()

Full status check

i = i + 1

return result

Yes

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