SH7721 datasheet(643/1524 Pages) RENESAS

Part #	SH7721

Description	Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

PDF	1524 Pages

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Manufacturer	RENESAS [Renesas Technology Corp]

Direct Link	http://www.renesas.com

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643 / 1524 page

Section 17 Realtime Clock (RTC)

Rev. 3.00 Jan. 18, 2008 Page 581 of 1458

REJ09B0033-0300

17.4.3

Reading Time

Figure 17.3 shows how to read the time.

Disable the carry interrupt

Clear the carry flag

Read counter register

Carry flag = 1?

Yes

Read counter register

interrupt

Disable the carry interrupt

Write 0 to CF in RCR1

(Set AF in RCR1 to 1 so that alarm

flag is not cleared.)

Read RCR1 and check CF bit

Write 1 to CIE in RCR1

Write 0 to CIE in RCR1

Clear the carry flag

Enable the carry interrupt

Clear the carry flag

Write 0 to CF in RCR1

(Set AF in RCR1 to 1 so that alarm

flag is not cleared.)

Read RCR1 and check CF bit

Write 0 to CIE in RCR1

To read the time

without using interrupts

(b) To use interrupts

(a)

Figure 17.3 Reading Time

If a carry occurs while reading the time, the correct time will not be obtained, so it must be read

again. Part (a) in figure 17.3 shows the method of reading the time without using interrupts; part

(b) in figure 17.3 shows the method using carry interrupts. To keep programming simple, method

(a) should normally be used.

SH7721 Datasheet(PDF) 643 Page - Renesas Technology Corp