參數(shù)資料
型號: MQ80C52TXXX-16SHXXX:RD
廠商: TEMIC SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 16 MHz, MICROCONTROLLER, CQFP44
文件頁數(shù): 15/83頁
文件大?。?/td> 8336K
16
8021G–AVR–03/11
ATmega329P/3290P
Figure 6-5.
Single Cycle ALU Operation
6.8
Reset and Interrupt Handling
The AtmelAVR provides several different interrupt sources. These interrupts and the separate
Reset Vector each have a separate program vector in the program memory space. All interrupts
are assigned individual enable bits which must be written logic one together with the Global
Interrupt Enable bit in the Status Register in order to enable the interrupt. Depending on the Pro-
gram Counter value, interrupts may be automatically disabled when Boot Lock bits BLB02 or
BLB12 are programmed. This feature improves software security. See the section ”Memory Pro-
The lowest addresses in the program memory space are by default defined as the Reset and
Interrupt Vectors. The complete list of vectors is shown in ”Interrupts” on page 53. The list also
determines the priority levels of the different interrupts. The lower the address the higher is the
priority level. RESET has the highest priority, and next is INT0 – the External Interrupt Request
0. The Interrupt Vectors can be moved to the start of the Boot Flash section by setting the IVSEL
bit in the MCU Control Register (MCUCR). Refer to ”Interrupts” on page 53 for more information.
The Reset Vector can also be moved to the start of the Boot Flash section by programming the
When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts are dis-
abled. The user software can write logic one to the I-bit to enable nested interrupts. All enabled
interrupts can then interrupt the current interrupt routine. The I-bit is automatically set when a
Return from Interrupt instruction – RETI – is executed.
There are basically two types of interrupts. The first type is triggered by an event that sets the
Interrupt Flag. For these interrupts, the Program Counter is vectored to the actual Interrupt Vec-
tor in order to execute the interrupt handling routine, and hardware clears the corresponding
Interrupt Flag. Interrupt Flags can also be cleared by writing a logic one to the flag bit position(s)
to be cleared. If an interrupt condition occurs while the corresponding interrupt enable bit is
cleared, the Interrupt Flag will be set and remembered until the interrupt is enabled, or the flag is
cleared by software. Similarly, if one or more interrupt conditions occur while the Global Interrupt
Enable bit is cleared, the corresponding Interrupt Flag(s) will be set and remembered until the
Global Interrupt Enable bit is set, and will then be executed by order of priority.
The second type of interrupts will trigger as long as the interrupt condition is present. These
interrupts do not necessarily have Interrupt Flags. If the interrupt condition disappears before the
interrupt is enabled, the interrupt will not be triggered.
When the AVR exits from an interrupt, it will always return to the main program and execute one
more instruction before any pending interrupt is served.
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
T1
T2
T3
T4
clk
CPU
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