基于STC89C51单片机，每当KEY按下时，将片内RAM30H单元的内容加1，利用外部中断1实现，请用C语言编程实现

Sure! Here's a C code snippet to implement the functionality you described using the STC89C51 microcontroller and external interrupt 1:

#include <reg51.h>

#define RAM_ADDRESS 0x30   // RAM address to increment

void externalInterrupt1() interrupt 2 {
    P3 = RAM_ADDRESS;     // Set the address to access RAM
    A = P0;               // Read the current value from RAM
    A++;                  // Increment the value
    P0 = A;               // Write the updated value back to RAM
}

void main() {
    IT1 = 1;              // Configure external interrupt 1 as falling edge triggered
    EX1 = 1;              // Enable external interrupt 1
    
    EA = 1;               // Enable global interrupts
    
    while(1) {
        // Your main code here
    }
}

In this code, we define the RAM address (`RAM_ADDRESS`) to be incremented as `0x30`. The `externalInterrupt1()` function is the interrupt service routine (ISR) for external interrupt 1. When the interrupt is triggered (i.e., when the KEY is pressed), this ISR is executed. Inside the ISR, we set `P3` to `RAM_ADDRESS` to access the desired RAM location. We read the current value from that location, increment it, and write the updated value back to RAM.

In the main function, we configure external interrupt 1 as falling edge triggered (`IT1 = 1`) and enable it (`EX1 = 1`). We also enable global interrupts (`EA = 1`). You can add your main code inside the while loop.

Please note that this code assumes you have already set up the necessary hardware connections and initializations for the microcontroller.