Hayes command set

what's it?

   It's also named as "AT Command".

   Details:

Special character

   AT - "Attention": tells the modem that modem-commands follow.
   Z - Resets the modem to its default state.
   CR - Carriage Return character (CR=\r=0x13): a command string is terminated with a Carriage Return character.

Mode

   1,data mode: in which the modem sends the data to the remote modem. (A modem in data mode treats everything it receives from the computer as data and sends it across the phone line).

   2,command mode: in which data is interpreted as commands to the local modem (commands that the local modem should execute).

S-寄存器

()

    调制解调器一般使用记忆存储区域或者S-寄存器来控制其操作环境的信息，S-寄存器是和联合使用的。

    要显示一个S-寄存器里的值，先输入ATSn?（也许是ATSn=？)

    要修改一个S-寄存器的值，先输入ATSn=r (n是该寄存器的序号，r是新值或者新的设置)

Mode切换

    从data mode 到 command mode: 发送(默认)字符串"+++",并pause一秒；

    从command mode 到 data mode: 发送命令ATO.