SH7751 Datasheet, PDF (409/1224 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

11.3.2 Time Reading Procedures
Figure 11.3 shows examples of the time reading procedures.
11. Realtime Clock (RTC)
Disable carry interrupts
Clear carry flag
Read counter register
Clear RCR1.CIE to 0
Clear RCR1.CF to 0
(Write 1 to RCR1.AF so that alarm flag
is not cleared)
Yes
Carry flag = 1?
No
Read RCR1 register and check CF bit
(a) Reading time without using interrupts
Clear carry flag
Enable carry interrupts
Clear carry flag
Read counter register
Set RCR1.CIE to 1
Clear RCR1.CF to 0
(Write 1 to RCR1.AF so that alarm flag
is not cleared)
Yes
Interrupt generated?
No
Disable carry interrupts
Clear RCR1.CIE to 0
(b) Reading time using interrupts
Figure 11.3 Examples of Time Reading Procedures
If a carry occurs while the time is being read, the correct time will not be obtained and the read
must be repeated. The procedure for reading the time without using interrupts is shown in figure
Rev.4.00 Oct. 10, 2008 Page 311 of 1122
REJ09B0370-0400