38
CHAPTER 5 CPU
●
Carry flag (C)
This flag is set to "1" when a carry from bit 7 or a borrow to bit 7 occurs as the result of an operation.
Otherwise, the flag is set to "0". When a shift instruction is executed, the flag is set to the shift-out value.
Figure 5.1-6 shows how the carry flag is updated by a shift instruction.
Figure 5.1-6 Carry Flag Updated by Shift Instruction
■
Interrupt Acceptance Control Bits
●
Interrupt enable flag (I)
When this flag is set to "1", interrupts are enabled and accepted by the CPU. When this flag is set to "0",
interrupts are disabled and rejected by the CPU.
The initial value after a reset is "0".
The SETI and CLRI instructions set and clear the flag to "1" and "0", respectively.
●
Interrupt level bits (IL1, IL0)
These bits indicate the level of the interrupt currently accepted by the CPU.
The interrupt level is compared with the value of the interrupt level setting register (ILR0 to ILR5) that
corresponds to the interrupt request (IRQ0 to IRQ23) of each peripheral resource.
The CPU services an interrupt request only when its interrupt level is smaller than the value of these bits
with the interrupt enable flag set (CCR: I = 1). Table 5.1-3 lists interrupt level priorities. The initial value
after a reset is "11
B
".
The interrupt level bits (IL1, IL0) are usually "11
B
" with the CPU not servicing an interrupt (with the main
program running).
For details on interrupts, see 8.1 Interrupts.
• Left-shift (ROLC)
• Right-shift (RORC)
bit7
bit0
bit7
bit0
C
C
Table 5.1-3 Interrupt Levels
IL1
IL0
Interrupt Level
Priority
0
0
0
High
0
1
1
1
0
2
1
1
3
Low (No interrupt)
Содержание F2 MC-8FX Family
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Страница 30: ...16 CHAPTER 1 DESCRIPTION 1 FPT 64P M23 FPT 64P M24 2 For the I O circuit type refer to 1 8 I O Circuit Type ...
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Страница 35: ...21 CHAPTER 2 HANDLING DEVICES This chapter gives notes on using 2 1 Device Handling Precautions ...
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Страница 39: ...25 CHAPTER 3 MEMORY SPACE This chapter describes memory space 3 1 Memory Space 3 2 Memory Map ...
Страница 43: ...29 CHAPTER 4 MEMORY ACCESS MODE This chapter describes the memory access mode 4 1 Memory Access Mode ...
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Страница 599: ...585 Pin Function Index V2 LCD power supply driving pin 2 439 V3 LCD power supply driving pin 3 439 ...
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