RX-8581SA/JE/NB,RA-8581SA

DC characteristic	Timing operation	Initial setting
Processing terminals	Setting register	Time and calendar
Access operation (READ/WRITE)	Timer interrupting function	Others

DC characteristic

Timing operation

Timing malfunction

Clock data is not renewed upon retrieval of clock data and the same time is always indicated, resulting in the data not being counted up from the start time. What are the potential causes?
We are using the RX-8581NB.

The internal quartz resonator may not be oscillating.

Potential causes are as follows:
-The metal end area (surrounded by a dotted circle) on the backside of the module is touching the substrate pattern, blocking the internal quartz resonator's oscillation.
-The internal quartz resonator is damaged due to a sudden impact such as being dropped.
The clock will not move if the internal quartz resonator does not oscillate, so the clock data being retrieved stays the same.

Initial setting

Processing terminals

Processing SCL and SDA terminals when backing up

Is it necessary to pull up the SDA and SCL terminals when backing up?

Pull-up is not necessary.

The SDA and SCL terminals can be used when they are floating (as well as VDD or GND level) during backup.
Make sure that an input terminal does not become an intermediate potential.

Setting register

Time and calendar

Access operation (READ/WRITE)

What is "Bus timeout function" regarding access?

The precautions for accessing indicate that when access takes 0.95 second or more, the internal BUS timeout function resets the I²C-BUS interface. Specifically, what state does it become?

Access state is forcibly terminated.

SCL and SDA of the module change to input state.
When writing, correct data cannot be written. In addition, /ACK will not respond.
When reading, everything can be read as 1 (=FFh).
Please reset start condition and address assignment to restart communication.

Timer interrupting function

Others