Preliminary document
Specifications in this document are tentative and subject to change.
Under development
R8C/34W Group, R8C/34X Group, R8C/34Y Group, R8C/34Z Group
2. Central Processing Unit (CPU)
2.8.7
Interrupt Enable Flag (I)
The I flag enables maskable interrupts.
Interrupt are disabled when the I flag is set to 0, and are enabled when the I flag is set to 1. The I flag is set to 0
when an interrupt request is acknowledged.
2.8.8
Stack Pointer Select Flag (U)
ISP is selected when the U flag is set to 0; USP is selected when the U flag is set to 1.
The U flag is set to 0 when a hardware interrupt request is acknowledged or the INT instruction of software
interrupt numbers 0 to 31 is executed.
2.8.9
Processor Interrupt Priority Level (IPL)
IPL is 3 bits wide and assigns processor interrupt priority levels from level 0 to level 7.
If a requested interrupt has higher priority than IPL, the interrupt is enabled.
2.8.10 Reserved Bit
If necessary, set to 0. When read, the content is undefined.
REJ03B0312-0010 Rev.0.10
Apr 09, 2010
Page 22 of 67
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