The most obvious issue is that the interface in Listing 6 requires a JNI call for each bit set or retrieved, as well as a JNI call to read a byte from, or write a byte to, the serial port.

最显著的一个问题就是，清单6中的接口在设置或检索每个位，以及从串行端口读取字节或者向串行端口写入字节都需要一个JNI调用。

youdao

Mode of serial port pair: synchronous clock device through the serial port read per second pair a serial output time information, serial port and RS232 interface and RS422 interface.

串行口对时方式：装置通过串行口读取同步时钟每秒一次的串行输出的时间信息对时，串行口又分为rs232接口和RS422接口方式。

youdao

This can be useful when polling a serial port for data, as your program can determine the number of bytes in the input buffer before attempting a read.

在查询串口是否有数据到来的时候这一段是很有用的，可以让程序在准备读取之前用来确定输入缓冲区里面的可读字节数。

youdao