R8C/1A Group, R8C/1B Group 2. Central Processing Unit (CPU)
Rev.1.30 Dec 08, 2006 Page 17 of 315
REJ09B0252-0130
2.8.7 Interrupt Enable Flag (I)
The I flag enables maskable interrupts.
Interrupts 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, 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.
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