參數(shù)資料
型號(hào)： IS89C51-12PL
廠商： INTEGRATED SILICON SOLUTION INC
元件分類(lèi)： 微控制器/微處理器
英文描述： 8-BIT, FLASH, 12 MHz, MICROCONTROLLER, PQCC44
封裝： PLASTIC, LCC-44
文件頁(yè)數(shù)： 22/48頁(yè)
文件大?。?/td> 371K
代理商： IS89C51-12PL
IS89C51
Integrated Silicon Solution, Inc. — 1-800-379-4774
29
MC016-1C
11/21/98
ISSI
Thus, the processor acknowledges an interrupt request by
executing a hardware-generated LCALL to the appropriate
servicing routine. In some cases it also clears the flag that
generated the interrupt, and in other cases it does not. It
never clears the Serial Port flags. This must be done in the
user's software. The processor clears an external interrupt
flag (IE0 or IE1) only if it was transition-activated. The
hardware-generated LCALL pushes the contents of the
Program Counter onto the stack (but it does not save the
PSW) and reloads the PC with an address that depends on
the source of the interrupt being serviced, as shown in the
following table.
Interrupt
Cleared by
Vector
Source
Request Bits
Hardware
Address
INT0
IE0
No (level)
0003H
Yes (trans.)
Timer 0
TF0
Yes
000BH
INT1
IE1
No (level)
0013H
Yes (trans.)
Timer 1
TF1
Yes
001BH
Serial Port
RI, TI
No
0023H
System
RST
0000H
Reset
Execution proceeds from that location until the RETI
instruction is encountered. The RETI instruction informs
the processor that this interrupt routine is no longer in
progress, then pops the top two bytes from the stack and
reloads the Program Counter. Execution of the interrupted
program continues from where it left off.
Note that a simple RET instruction would also have returned
execution to the interrupted program, but it would have left
the interrupt control system thinking an interrupt was still in
progress.
SFR Register and
Interrupt
Flag
Bit Position
External 0
IE0
TCON.1
External 1
IE1
TCON.3
Timer 1
TF1
TCON.7
Timer 0
TF0
TCON.5
Serial Port
TI
SCON.1
Serial Port
RI
SCON.0
When an interrupt is accepted, the following action occurs:
1. The current instruction completes operation.
2. The PC is saved on the stack.
3. The current interrupt status is saved internally.
4. Interrupts are blocked at the level of the interrupts.
5. The PC is loaded with the vector address of the ISR
(interrupts service routine).
6. The ISR executes.
The ISR executes and takes action in response to the
interrupt. The ISR finishes with RETI (return from interrupt)
instruction. This retrieves the old value of the PC from the
stack and restores the old interrupt status. Execution of the
main program continues where it left off.
External Interrupts
The external sources can be programmed to be level-
activated or transition-activated by setting or clearing bit
IT1 or IT0 in Register TCON. If ITx= 0, external interrupt x
is triggered by a detected low at the
INTx pin. If ITx = 1,
external interrupt x is edge-triggered. In this mode if
successive samples of the
INTx pin show a high in one
cycle and a low in the next cycle, interrupt request flag IEx
in TCON is set. Flag bit IEx then requests the interrupt.
Since the external interrupt pins are sampled once each
machine cycle, an input high or low should hold for at least
12 oscillator periods to ensure sampling. If the external
interrupt is transition-activated, the external source has to
hold the request pin high for at least one machine cycle,
and then hold it low for at least one machine cycle to
ensure that the transition is seen so that interrupt request
flag IEx will be set. IEx will be automatically cleared by the
CPU when the service routine is called.
If the external interrupt is level-activated, the external
source has to hold the request active until the requested
interrupt is actually generated. Then the external source
must deactivate the request before the interrupt service
routine is completed, or else another interrupt will be
generated.
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參數(shù)描述
IS89C51-12PLI 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:8-Bit Microcontroller
IS89C51-12PQ 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:8-Bit Microcontroller
IS89C51-12PQI 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:8-Bit Microcontroller
IS89C51-12W 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:8-Bit Microcontroller
IS89C51-12WI 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:8-Bit Microcontroller
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