參數(shù)資料
型號(hào): AT89LV55-12PI
廠商: Atmel
文件頁數(shù): 6/32頁
文件大?。?/td> 0K
描述: IC 8051 MCU FLASH 20K 40DIP
標(biāo)準(zhǔn)包裝: 10
系列: 89LV
核心處理器: 8051
芯體尺寸: 8-位
速度: 12MHz
連通性: UART/USART
輸入/輸出數(shù): 32
程序存儲(chǔ)器容量: 20KB(20K x 8)
程序存儲(chǔ)器類型: 閃存
RAM 容量: 256 x 8
電壓 - 電源 (Vcc/Vdd): 2.7 V ~ 6 V
振蕩器型: 內(nèi)部
工作溫度: -40°C ~ 85°C
封裝/外殼: 40-DIP(0.600",15.24mm)
包裝: 管件
14
0811E–MICRO–9/08
AT89LV55
12. Interrupts
The AT89LV55 has a total of six interrupt vectors: two external interrupts (INT0 and INT1), three
timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These interrupts are all shown
Each of these interrupt sources can be individually enabled or disabled by setting or clearing a
bit in Special Function Register IE. IE also contains a global disable bit, EA, which disables all
interrupts at once.
Note that Table 12-1 shows that bit position IE.6 is unimplemented. In the AT89C51 and
AT89LV51, bit position IE.5 is also unimplemented. User software should not write 1s to these
bit positions, since they may be used in future AT89 products.
Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register T2CON. Nei-
ther of these flags is cleared by hardware when the service routine is vectored to. In fact, the
service routine may have to determine whether it was TF2 or EXF2 that generated the interrupt,
and that bit will have to be cleared in software.
The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in which the timers
overflow. The values are then polled by the circuitry in the next cycle. However, the Timer 2 flag,
TF2, is set at S2P2 and is polled in the same cycle in which the timer overflows. For further infor-
mation, see the Microcontroller Data Book, section titled “Interrupts.”
Table 12-1.
Interrupt Enable (IE) Register
(MSB)
(LSB)
EA
ET2
ES
ET1
EX1
ET0
EX0
Enable Bit = 1 enables the interrupt.
Enable Bit = 0 disables the interrupt.
Symbol
Position
Function
EA
IE.7
Disables all interrupts. If EA = 0, no interrupt is acknowledged. If EA = 1, each
interrupt source is individually enabled or disabled by setting or clearing its
enable bit.
IE.6
Reserved.
ET2
IE.5
Timer 2 interrupt enable bit.
ES
IE.4
Serial Port interrupt enable bit.
ET1
IE.3
Timer 1 interrupt enable bit.
EX1
IE.2
External interrupt 1 enable bit.
ET0
IE.1
Timer 0 interrupt enable bit.
EX0
IE.0
External interrupt 0 enable bit.
User software should never write 1s to unimplemented bits, because they may be used in future AT89 products.
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