HD6433937 Datasheet, PDF (265/521 Pages) Hitachi Semiconductor – Hardware Manual

10.2.5 Application Note
(1) Conditions for use of SCI1 in subactive mode and subsleep mode
In subactive or subsleep mode, SCI1 can be used only when the CPU operation clock is ø_W/2.
(2) Confirming the end of serial transfer
Do not read or write to SCSR1 during serial transfer.
The following two methods can be used to confirm the end of serial transfer:
(a) Using SCI1 interrupt exception handling
Set the IENS1 bit to 1 in IENR1 and execute interrupt exception handling.
(b) Performing IRR1 polling
With SCI1 interrupts disabled (IENS1 = 0 in IENR1), confirm that the IRRS1 bit in IRR1
has been set to 1.
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