This web page will give you basic information about parallel port.
A parallel port is a type of interface found on PC for connecting various peripherals.Commonly it is known as printer port.
Pinout of D-type 25 pin parallel port connector
Pins with * symbol indicates hardware inversion i.e if a pin has low logic level,corresponding bit in the register will have value 1.
Signals with prefix 'n' are active low .
Port Address
The parallel Port has three commonly used base addresses.
Corresponding to base address of parallel port the data,status and control registers will have the following addresses.
Parallel Port Registers
Parallel Port has three register.
1.Data Register (Base+0)
It is used for sending data on the parallel Port's data lines (Pins 2-9).If your port is bi-directional you can receive data on this address.
2 .Status Register (Base+1)
It is used to read the status of signals given by peripheral device to parallel port.It is made up of 5 input lines.Any data written to this port will be ignored.It is read only register
3.Control Register (Base+2)
It is used to give control signals to peripheral device.It is made up of 4 output lines.It is write only register.
The output of the Parallel Port is normally TTL logic levels.The current you can sink and source varies from
port to port. Most Parallel Ports implemented in ASIC, can sink and source
around 12mA.The best bet is
to use a buffer, so the least current is drawn from the Parallel Port.
Hence to make your parallel port talk you have to use data,status and control register according to communication protocol of peripheral device.
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