Expansion of External Interrupt Sources of MCU

Case analysis:
The method of combining interrupt and query is to sort multiple external interrupt sources in the system according to their importance, connect the highest-level interrupt source to an external interrupt source input terminal of MCS-51 (for example, to a pin), and connect the remaining interrupt sources to another external interrupt input terminal ( ) by wire "OR" method, and connect to an I/O port at the same time, such as P1 port as shown in Figure 3. The interrupt request is generated by the hardware circuit, and the identification of the interrupt source is processed by program query. The query order is determined by the priority of the interrupt source. Figure 3 shows the connection circuit of five external interrupt sources, in which devices 1~4 are connected through OC gates and connected to P1.0~P1.3, all using level triggering. Device 0 is the highest-level interrupt source and is used as the input signal of external interrupt 0 alone. This method is relatively simple to expand, but when the number of external interrupt expansions is large, the query time is relatively long, resulting in low program execution efficiency.
Program code:
ORG 1000H
LJMP INTR
INTR: PUSH PSW ; protect context
PUSH A 
JNB P1.0, IR1 ; P1.0 pin is 0, jump to device 1 interrupt service routine
JNB P1.1, IR2 ; P1.1 pin is 0, jump to device 2 interrupt service routine
JNB P1.2, IR3 ; P1.2 pin is 0, jump to device 3 interrupt service routine
JNB P1.3, IR4 ; P1.3 pin is 0, jump to device 4 interrupt service routine
INTR1: POP A ; restore context
POP PSW 
RETI ; interrupt return
IR1: …… ; device 1 interrupt service routine entry
AJMP INTR1 ; jump to the instruction indicated by INTR1
IR2: …… ; device 2 interrupt service routine entry
AJMP INTR1 ; jump to INTR1
IR3: …… ; device 3 interrupt service routine entry
AJMP INTR1 ; Jump to INTR1
IR4: ... ; Device 4 interrupt service routine entry
AJMP INTR1 ; Jump to INTR1