
Rev.0.10 Mar 4, 2004 Page 10 of 16
REJ03B0078-0010Z
Under development
R8C/15 Group 2. Central Processing Unit (CPU)
Preliminary specification
Specications in this manual are tentative and subject to change.
2.8.7 Interrupt Enable Flag (I Flag)
This flag enables a maskable interrupt.
Maskable interrupts are disabled when the I flag is “0”, and are enabled when the I flag is “1”. The I
flag is cleared to “0” when the interrupt request is accepted.
2.8.8 Stack Pointer Select Flag (U Flag)
ISP is selected when the U flag is “0”; USP is selected when the U flag is “1”.
The U flag is cleared to “0” when a hardware interrupt request is accepted or an INT instruction for
software interrupt Nos. 0 to 31 is executed.
2.8.9 Processor Interrupt Priority Level (IPL)
IPL is configured with three bits, for specification of up to eight processor interrupt priority levels from
level 0 to level 7.
If a requested interrupt has priority greater than IPL, the interrupt is enabled.
2.8.10 Reserved Area
When write to this bit, write “0”. When read, its content is indeterminate.
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