Parallel Ports
The parallel port as we know it was originally designed by Centronics Data Computer Corporation.
Therefore, you will sometimes hear the parallel port described as the “Centronics” port or interface.
The parallel port, in contrast to the serial port, has eight data lines, or 8-bits in “parallel”.
| Bits | Name | Description |
|---|---|---|
| 0:2 | Unused | Unused |
| 3 | ERROR | 0: The printer has encountered an error condition. 1: The printer reports no current error condition. |
| 4 | SLCT | 0: The printer has not been selected (Printer offline) 1: The printer has been selected (Select/Online button pressed) |
| 5 | PE | 0: The printer reports it has paper. 1: The printer reports it is out of paper. |
| 6 | ACK | 0: The printer has acknowledged the last character and is ready to receive another. 1: The printer is processing (busy). |
| 7 | BUSY | 0: The printer is busy and cannot accept data. 1: The printer is not busy and can receive data. |
| Bits | Name | Description |
|---|---|---|
| 0 | STR | Data clock strobe to feed data into the printer. |
| 1 | ALF | 0: Do not line-feed automatically. 1: Line-feed automatically. |
| 2 | INIT | 0: Initialize the printer. 1: Do nothing. |
| 3 | SLCT_IN | 0: Leave printer unselected. 1: Select the printer. |
| 4 | IRQEN | 0: Disable interrupts. 1: Enable interrupts triggered by a rising edge of the /ACK pin. |
| 5:7 | Unused | Unused |