
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 
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.