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#SERIAL PORT COMPONENT FOR LAZARUS PIT WIKI SERIAL#If you want to use the serial port for communications, you first have to initialize it. Programming the Serial Communications Port Serial ports are useful for transferring information between systems when other more traditional methods are unavailable. When the system itself is in danger of potentially crashing at times, it's nice to get debugging outputs safe to another computer before the test system triple-faults. You can operate the computer without a monitor, keyboard or mouse and instead use the serial port as a console using a protocol such as TTY or VT100. This involves writing a stub for GDB within your OS. ![]() You can use the serial port to connect to a host computer, and use the GDB debugger to debug your operating system. The receiving end of the device has the wires switched and it has a female port, which means you can plug a male plug into it.ĭuring the early stages of kernel development, you might wonder why you would bother writing a serial driver. This can be done in the cable itself, or as an extension called a Null Modemįor serial devices, you don't need to setup the cable this way. The cable needs to have its transmit-receive wires and it's handshaking wires switched.The cable needs to have two female plugs so it can plug into both computers.If you want to connect two computers, you need two things in your cable: Today there is duplex mode, but the handshaking pins are still used. The other device would then use another handshaking pin to tell it to send whatever it wanted to send. In the past, there was no duplex mode, so if a computer wanted to send something it had to tell the other device or computer that it was about to transmit, using one of the hardware handshaking pins. There are a few other pins, used for hardware handshaking. Most serial ports run in a duplex mode-that is, they can send and receive simultaneously. There is a transmitting pin (for sending information away) and a receiving pin (for getting information). A DB-25 has most of the pins as ground pins or simply unconnected, whereas a DE-9 has only one ground pin. This Wikipedia page has more information on the plug used.īoth have the same basic types of pins. They plug in to your computer using a female plug (unless your computer is odd and has a female port, in which case your cable will need a male plug). The 9-pin ones are called DE-9 (or more commonly, DB-9 even though DE-9 is its technical name) and the 25-pin ones are called DB-25. 9-pin is smaller and is used more often though in the past the 25-pin ones were used more often. 25-pin ports are not any better, they just have more pins (most unused) and are bigger. There are actually two kinds of serial port: 25-pin and 9-pin. ![]() The Wikipedia page on Serial ports has a lot of information, and it is summarised here.
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