Usage Notes; Register Writing During Count Operation; Use Of Realtime Clock Periodic Interrupts; Transition To Standby Mode After Setting Register - Renesas RZ/A Series User Manual

RZ/A1L Group, RZ/A1LU Group, RZ/A1LC Group
13.5

Usage Notes

13.5.1

Register Writing during Count Operation

The following registers cannot be written to during count operation (while the START bit = 1 in RCR2).
RSECCNT, RMINCNT, RHRCNT, RDAYCNT, RWKCNT, RMONCNT, RYRCONT
Count operation must be stopped before writing to any of the above registers.
13.5.2

Use of Realtime Clock Periodic Interrupts

The method of using the periodic interrupt function is shown in Figure 13.5.
A periodic interrupt can be generated periodically at the interval set by bits PES2 to PES0 in RCR2. When the time set by
bits PES2 to PES0 has elapsed, the PEF is set to 1.
The PEF is cleared to 0 upon periodic interrupt generation or when bits PES2 to PES0 are set. Periodic interrupt
generation can be confirmed by reading this bit, but normally the interrupt function is used.
Figure 13.5 Using Periodic Interrupt Function
13.5.3

Transition to Standby Mode after Setting Register

When a transition to standby mode is made after registers in this module are set, sometimes counting is not performed
correctly. After the registers are set, be sure to perform one dummy read of the registers before making a transition to
standby mode.
13.5.4

Usage Notes when Writing to and Reading the Register

• After writing to the RCR2 register or any of the counters such as the second counter, dummy-read the register twice
before reading the actual value. The register contents before the write are returned by the two dummy reads, and the
third read returns the register contents reflecting the write.
• Registers other than the above can be read immediately after a write and the written value is reflected.
R01UH0437EJ0600 Rev.6.00
Jan 29, 2021
Set PES, clear PEF
Elapse of time set by PES
Clear PEF
Set PES2 to PES0
and clear PEF to 0
in RCR2
Clear PEF to 0
13. Realtime Clock
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