PD17225_15 Datasheet, PDF (23/86 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLER FOR SMALL GENERAL-PURPOSE INFRARED REMOTE CONTROL TRANSMITTER

µPD17225, 17226, 17227, 17228
(3) Note on using data buffer
When transferring data to/from the peripheral hardware via the data buffer, the unused peripheral addresses,
write-only peripheral registers (only when executing PUT), and read-only peripheral registers (only when
executing GET) must be handled as follows:
• When device operates
Nothing changes even if data is written to the read-only register.
If the unused address is read, an undefined value is read. Nothing changes even if data is written to that
address.
• Using assembler
An error occurs if an instruction is executed to read a write-only register.
Again, an error occurs if an instruction is executed to write data to a read-only register.
An error also occurs if an instruction is executed to read or write an unused address.
• If an in-circuit emulator (IE-17K or IE-17K-ET) is used (when instruction is executed for patch processing)
An undefined value is read if an attempt is made to read the data of a write-only register, but an error does
not occur.
Nothing changes even if data is written to a read-only register, and an error does not occur.
An undefined value is read if an unused address is read; nothing changes even if data is written to this
address. An error does not occur.
Data Sheet U12643EJ2V0DS00
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