You can see the parallel port connector in the rear panel of your PC. It is a 25 pin female (DB25) connector (to which printer is connected). On almost all the PCs only one parallel port is present, but you can add more by inserting ISA/PCI parallel port cards.
The pin outs of DB25 connector is shown in the picture below
The pin outs of DB25 connector is shown in the picture below
The lines in DB25 connector are divided in to three groups, they are
1. Data bus
2. Control bus
3. Status bus
The details of parallel port signal lines are given below
Register Address
The details of parallel port signal lines are given below
| Pin Number | Signal name | Direction | Register Bit | Inverted |
| 1 | nStrobe | Out | Control-0 | Yes |
| 2 | Data0 | In/Out | Data-0 | No |
| 3 | Data1 | In/Out | Data-1 | No |
| 4 | Data2 | In/Out | Data-2 | No |
| 5 | Data3 | In/Out | Data-3 | No |
| 6 | Data4 | In/Out | Data-4 | No |
| 7 | Data5 | In/Out | Data-5 | No |
| 8 | Data6 | In/Out | Data-6 | No |
| 9 | Data7 | In/Out | Data-7 | No |
| 10 | nAck | In | Status-6 | No |
| 11 | Busy | In | Status-7 | Yes |
| 12 | Paper-Out | In | Status-5 | No |
| 13 | Select | In | Status-4 | No |
| 14 | Linefeed | Out | Control-1 | Yes |
| 15 | nError | In | Status-3 | No |
| 16 | nInitialize | Out | Control-2 | No |
| 17 | nSelect-Printer | Out | Control-3 | Yes |
| 18-25 | Ground | - | - | - |
Register Address
| Register | LPT1 | LPT2 |
| data registar(baseaddress + 0) | 0x378 | 0x278 |
| status register (baseaddress + 1) | 0x379 | 0x279 |
| control register (baseaddress + 2) | 0x37a | 0x27a |
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