Rainbow Electronics DS89C450 - Manual (Page 37)

DS89C430/DS89C440/DS89C450 Ultra-High-Speed Flash Microcontrollers
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Interrupt Priority
There are five levels of interrupt priority: Level 4 to 0. The highest interrupt priority is level 4, which is reserved for
the power-fail interrupt. All other interrupts have individual priority bits in the interrupt priority registers to allow each
interrupt to be assigned a priority level from 3 to 0. The power-fail interrupt always has the highest priority if it is
enabled. All interrupts also have a natural hierarchy. In this manner, when a set of interrupts has been assigned the
same priority, a second hierarchy determines which interrupt is allowed to take precedence. The natural hierarchy
is determined by analyzing potential interrupts in a sequential manner with the order listed in
Table 12 .
The processor indicates that an interrupt condition occurred by setting the respective flag bit. This bit is set
regardless of whether the interrupt is enabled or disabled. Unless marked in
Table 12 , all these flags must be
cleared by software.
Table 12. Interrupt Summary
INTERRUPT VECTOR NATURAL ORDER FLAG ENABLE PRIORITY CONTROL
Power Fail 33h 0 (Highest) PFI (WDCON.4) EPFI(WDCON.5) N/A
External Interrupt 0 03h 1 IE0 (TCON.1) (Note 1) EX0 (IE.0)
LPX0 (IP0.0);
MPX0 (IP1.0)
Timer 0 Overflow 0Bh 2 TF0 (TCON.5) (Note 2) ET0 (IE.1)
LPT0 (IP0.1);
MPT0 (IP1.1)
External Interrupt 1 13h 3 IE1 (TCON.3) (Note 1) EX1 (IE.2)
LPX1 (IP0.2);
MPX1 (IP1.2)
Timer 1 Overflow 1Bh 4 TF1 (TCON.7) (Note 2) ET1 (IE.3)
LPT1 (IP0.3);
MPT1 (IP1.3)
Serial Port 0 23h 5
RI_0 (SCON0.0);
TI_0 (SCON0.1)
ES0 (IE.4)
LPS0 (IP0.4);
MPS0 (IP1.4)
Timer 2 Overflow 2Bh 6
TF2 (T2CON.7);
EXF2 (T2CON.6)
ET2 (IE.5)
LPT2 (IP0.5);
MPT2 (IP1.5)
Serial Port 1 3Bh 7
RI_1 (SCON1.0);
TI_1 (SCON1.1)
ES1 (IE.6)
LPS1 (IP0.6);
MPS1 (IP1.6)
External Interrupt 2 43h 8 IE2 (EXIF.4) EX2 (EIE.0)
LPX2 (EIP0.0);
MPX2 (EIP1.0)
External Interrupt 3 4Bh 9 IE3 (EXIF.5) EX3 (EIE.1)
LPX3 (EIP0.1);
MPX3 (EIP1.1)
External Interrupt 4 53h 10 IE4 (EXIF.6) EX4 (EIE.2)
LPX4 (EIP0.2);
MPX4 (EIP1.2)
External Interrupt 5 5Bh 11 IE5 (EXIF.7) EX5 (EIE.3)
LPX5 (EIP0.3);
MPX5 (EIP1.3)
Watchdog 63h 12 (Lowest) WDIF (WDCON.3) EWDI (EIE.4)
LPWDI (EIP0.4);
MPWDI (EIP1.4)
Note 1: If the interrupt is edge triggered, the flag is cleared automatically by hardware when the service routine is vectored to. If the interrupt
is level triggered, the flag follows the state of the pin.
Note 2: The flag is cleared automatically by hardware when the service routine is vectored to.