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参数资料
| 型号： | ST72121J2T3/XXX |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 8-BIT, MROM, 8 MHz, MICROCONTROLLER, PQFP44 |
| 封装： | PLASTIC, TQFP-44 |
| 文件页数： | 9/87页 |
| 文件大小： | 1365K |
| 代理商： | ST72121J2T3/XXX |
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ST72121
3.3 INTERRUPTS
The ST7 core may be interrupted by one of two dif-
ferent methods: maskable hardware interrupts as
listed in the Interrupt Mapping Table and a non-
maskable software interrupt (TRAP). The Interrupt
processing flowchart is shown in Figure 14.
The maskable interrupts must be enabled clearing
the I bit in order to be serviced. However, disabled
interrupts may be latched and processed when
they are enabled (see external interrupts subsec-
tion).
When an interrupt has to be serviced:
– Normal processing is suspended at the end of
the current instruction execution.
– The PC, X, A and CC registers are saved onto
the stack.
– The I bit of the CC register is set to prevent addi-
tional interrupts.
– The PC is then loaded with the interrupt vector of
the interrupt to service and the first instruction of
the interrupt service routine is fetched (refer to
the Interrupt Mapping Table for vector address-
es).
The interrupt service routine should finish with the
IRET instruction which causes the contents of the
saved registers to be recovered from the stack.
Note: As a consequence of the IRET instruction,
the I bit will be cleared and the main program will
resume.
Priority management
By default, a servicing interrupt can not be inter-
rupted because the I bit is set by hardware enter-
ing in interrupt routine.
In the case several interrupts are simultaneously
pending, an hardware priority defines which one
will be serviced first (see the Interrupt Mapping Ta-
ble).
Non Maskable Software Interrupts
This interrupt is entered when the TRAP instruc-
tion is executed regardless of the state of the I bit.
It will be serviced according to the flowchart on
Figure 14.
Interrupts and Low power mode
All interrupts allow the processor to leave the Wait
low power mode. Only external and specific men-
tioned interrupts allow the processor to leave the
Halt low power mode (refer to the “Exit from HALT“
column in the Interrupt Mapping Table).
External Interrupts
External interrupt vectors can be loaded in the PC
register if the corresponding external interrupt oc-
curred and if the I bit is cleared. These interrupts
allow the processor to leave the Halt low power
mode.
The external interrupt polarity is selected through
the miscellaneous register or interrupt register (if
available).
External interrupt triggered on edge will be latched
and the interrupt request automatically cleared
upon entering the interrupt service routine.
If more than one input pin of a group connected to
the same interrupt line is selected simultaneously,
this will be logically ORed.
Warning: Thetypeof sensitivity definedinthe
Miscellaneous or Interrupt register (if available)
applies tothe EI source.IncaseofanORed
source (as described on the I/O ports section). A
low level on an I/O pin configured as input with in-
terrupt, masks the interrupt request even in case
of rising-edge sensitivity.
Peripheral Interrupts
Different peripheral interrupt flags in the status
register are able to cause an interrupt when they
are active if both:
– The I bit of the CC register is cleared.
– The corresponding enable bit is set in the control
register.
If any of these two conditions is false, the interrupt
is latched and thus remains pending.
Clearing an interrupt request is done by:
– writing “0” to the corresponding bit in the status
register or
– an access to the status register while the flag is
set followed by a read or write of an associated
register.
Note: the clearing sequence resets the internal
latch. A pending interrupt (i.e. waiting for being en-
abled) will therefore be lost if the clear sequence is
executed.
17
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相关代理商/技术参数 |
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| ST72121J4 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:8-BIT MICROCONTROLLER (MCU) WITH 8 TO 16 K ROM/OTP/EPROM. 384 TO 512 BYTES RAM. WDG. SCI. SPI & 2 TIMERS - SDIP42. TQFP44 |
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| ST72124J2 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES |
| ST72124J2B | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES |
| ST72124J2B1 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES |
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