DF2211NP24V Renesas Technology / Hitachi Semiconductor, DF2211NP24V Datasheet - Page 413

• Manufacturer Part Number: DF2211NP24V
• Description: H8S/2200 Series, 2212 Group, USB, RTC, HSS TNP-64B; Vcc= 2.7 to 3.6 volts, Temp= -20 to 75 C; Package: PVQN0064LB-A
• Manufacturer: Renesas Technology / Hitachi Semiconductor

11.4.2
When the seconds, minutes, hours, or day-of-week datum is updated while time data is being read,
the data obtained may not be correct, and so the time data must be read again. Figure 11.4 shows
an example in which correct data is not obtained. In this example, since only RSECDR is read
after data update, about 1-minute inconsistency occurs.
To avoid reading in this timing, the following processing must be performed.
1. Check the setting of the BSY bit, and when the BSY bit changes from 1 to 0, read from the
2. Making use of interrupts, read from the second, minute, hour, and day-of week registers after
3. Read from the second, minute, hour, and day-of week registers twice in a row, and if there is
second, minute, hour, and day-of-week registers. When about 62.5 ms is passed after the BSY
bit is set to 1, the registers are updated, and the BSY bit is cleared to 0.
the IRQ5F flag in ISR is set to 1 and the BSY bit is confirmed to be 0.
no change in the read data, the read data is used.
Time Data Reading Procedure
Figure 11.4 Example: Reading of Inaccurate Time Data
Before update
After update
BSY bit = 0
BSY bit -> 1 (under data update)
BSY bit -> 0
(1) Day-of-week data register read H'03
(2) Hour data register read
(3) Minute data register read
(4) Second data register read
RWKDR = H'03, RHDDR = H'13, RMINDR = H'47, RSECDR = H'00
RWKDR = H'03, RHDDR = H'13, RMINDR = H'46, RSECDR = H'59
H'00
H'13
H'46
Rev.7.00 Dec. 24, 2008 Page 359 of 698
REJ09B0074-0700