What is a null modem in windbg ?

[leechat2001]

what is a null modem

In kernel debugging for windows 2000 I am using windbg.
I don't know what is a null modem...! can any one please help...!


Please give me links to study further about windbg ( windows debugger) and the kd.exe ( kernel debugger)


Please help...!

Thanks
leechat2001

 

[barrybear]

Re: what is a null modem

I have only heard this expresion used when refering to a serial port cable, that you would use connect a modem up to a computer via the serial port.
It is a refrence to the way the signal cable is wired as opposed to a standard serial cable.

Barrybear

 

[M!k]

Re: what is a null modem

The purpose of a null-modem cable is to permit two RS-232 "DTE" devices to communicate with each other without modems or other communication devices (i.e., "DCE"s) between them.

For debugging purposes you'll need such a cable to connect the PC running the debugger to the PC running the application you're developing.
Read the whole text incl. connection tables here:
http://www.nullmodem.com/NullModem.htm


Mik

 

[Big Boy]

Re: what is a null modem

In simple words, it's a simple RS232 cable (serial port cable) in which wires are crossed. You connect such cable between 2 PC directly, or it can also connected between 2 serial ports of a single computer.

If would use a simple cable, with straight wires, that is pin 1 of one serial port goes to pin 1 of the other serial port, pin 2 goes to pin 2, ... then is won't work because on both serial ports, the transmit pin is the same and the receive pin is the same. You need data comming out of the Tx (transmit) pin going to the Rx (receive) pin of the other serial port, and vice-versa. Same is true for some other pins, like CTS and RTS, ... So the cable cross those wire.

On the 2 PC, it look to them as if there were connected via a modem, which would already be connected, except that there really is none, just a direct connection. From there the expression NULL-modem.