参数资料
型号: P87C52X2FN,112
厂商: NXP Semiconductors
文件页数: 27/62页
文件大小: 0K
描述: IC 80C51 MCU 256 RAM 40DIP
产品培训模块: Migrating from 8/16-Bit MCUs to 32-Bit ARMs
标准包装: 9
系列: 87C
核心处理器: 8051
芯体尺寸: 8-位
速度: 33MHz
连通性: EBI/EMI,UART/USART
外围设备: POR
输入/输出数: 32
程序存储器容量: 8KB(8K x 8)
程序存储器类型: OTP
RAM 容量: 256 x 8
电压 - 电源 (Vcc/Vdd): 2.7 V ~ 5.5 V
振荡器型: 内部
工作温度: -40°C ~ 85°C
封装/外壳: 40-DIP(0.600",15.24mm)
包装: 管件
其它名称: 568-7912-5
568-7912-5-ND
568-8361-5
935269602112
P87C52X2FN
P87C52X2FN,112-ND
P87C52X2FN-ND
Philips Semiconductors
Product data
P80C3xX2; P80C5xX2;
P87C5xX2
80C51 8-bit microcontroller family
4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V),
low power, high speed (30/33 MHz)
2003 Jan 24
33
Interrupt Priority Structure
IE0
IE1
INT0
IT0
TF0
INT1
IT1
TF1
RI
TI
Interrupt
Sources
0
1
0
1
SU01521
TF2, EXF2
Figure 21. Interrupt Sources
Interrupts
The devices described in this data sheet provide six interrupt
sources. These are shown in Figure 21. The External Interrupts
INT0 and INT1 can each be either level-activated or
transition-activated, depending on bits IT0 and IT1 in Register
TCON. The flags that actually generate these interrupts are bits IE0
and IE1 in TCON. When an external interrupt is generated, the flag
that generated it is cleared by the hardware when the service routine
is vectored to only if the interrupt was transition-activated. If the
interrupt was level-activated, then the external requesting source is
what controls the request flag, rather than the on-chip hardware.
The Timer 0 and Timer 1 Interrupts are generated by TF0 and TF1,
which are set by a rollover in their respective Timer/Counter
registers (except see Timer 0 in Mode 3). When a timer interrupt is
generated, the flag that generated it is cleared by the on-chip
hardware when the service routine is vectored to.
The Serial Port Interrupt is generated by the logical OR of RI and TI.
Neither of these flags is cleared by hardware when the service
routine is vectored to. In fact, the service routine will normally have
to determine whether it was RI or TI that generated the interrupt,
and the bit will have to be cleared in software.
All of the bits that generate interrupts can be set or cleared by
software, with the same result as though it had been set or cleared
by hardware. That is, interrupts can be generated or pending
interrupts can be canceled in software.
Each of these interrupt sources can be individually enabled or
disabled by setting or clearing a bit in Special Function Register IE
(Figure 22). IE also contains a global disable bit, EA, which disables
all interrupts at once.
Priority Level Structure
Each interrupt source can also be individually programmed to one of
four priority levels by setting or clearing bits in Special Function
Registers IP (Figure 23) and IPH (Figure 24). A lower-priority
interrupt can itself be interrupted by a higher-priority interrupt, but
not by another interrupt of the same level. A high-priority level 3
interrupt can’t be interrupted by any other interrupt source.
If two request of different priority levels are received simultaneously,
the request of higher priority level is serviced. If requests of the
same priority level are received simultaneously, an internal polling
sequence determines which request is serviced. Thus within each
priority level there is a second priority structure determined by the
polling sequence as follows:
Source
Priority Within Level
1. IE0 (External Int 0)
(highest)
2. TF0 (Timer 0)
3. IE1 (External Int 1)
4. TF1 (Timer 1)
5. RI+TI (UART)
6. TF2, EXF2 (Timer 2)
(lowest)
Note that the “priority within level” structure is only used to resolve
simultaneous requests of the same priority level.
The IP and IPH registers contain a number of unimplemented bits.
User software should not write 1s to these positions, since they may
be used in other 80C51 Family products.
How Interrupts Are Handled
The interrupt flags are sampled at S5P2 of every machine cycle.
The samples are polled during the following machine cycle. If one of
the flags was in a set condition at S5P2 of the preceding cycle, the
polling cycle will find it and the interrupt system will generate an
LCALL to the appropriate service routine, provided this
hardware-generated LCALL is not blocked by any of the following
conditions:
1. An interrupt of equal or higher priority level is already in
progress.
2. The current (polling) cycle is not the final cycle in the execution
of the instruction in progress.
3. The instruction in progress is RETI or any write to the IE or IP
registers.
Any of these three conditions will block the generation of the LCALL
to the interrupt service routine. Condition 2 ensures that the
instruction in progress will be completed before vectoring to any
service routine. Condition 3 ensures that if the instruction in
progress is RETI or any access to IE or IP, then at least one more
instruction will be executed before any interrupt is vectored to.
The polling cycle is repeated with each machine cycle, and the
values polled are the values that were present at S5P2 of the
previous machine cycle. Note that if an interrupt flag is active but not
being responded to for one of the above conditions, if the flag is not
still active when the blocking condition is removed, the denied
interrupt will not be serviced. In other words, the fact that the
interrupt flag was once active but not serviced is not remembered.
Every polling cycle is new.
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