Input/Output Interfaces
Parallel Interface Control
The BIOS function INT 17 provides simplified control of the parallel interface. Basic functions such as initialization, character printing, and printer status are provide by subfunctions of INT
17.The parallel interface is controllable by software through a set of I/O mapped registers. The number and type of registers available depends on the mode used (SPP, EPP, or ECP). Table
Table
Parallel Interface Control Registers
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| SPP | EPP | ECP |
I/O |
| Mode | Mode | Mode |
Address | Register | Ports | Ports | Ports |
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Base | Data | LPT1,2,3 | LPT1,2 | LPT1,2,3 |
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Base + 1h | Printer Status | LPT1,2,3 | LPT1,2 | LPT1,2,3 |
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Base + 2h | Control | LPT1,2,3 | LPT1,2 | LPT1,2,3 |
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Base + 3h | Address | LPT1,2 | ||
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Base + 4h | Data Port 0 | LPT1,2 | ||
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Base + 5h | Data Port 1 | LPT1,2 | ||
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Base + 6h | Data Port 2 | LPT1,2 | ||
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Base + 7h | Data Port 3 | LPT1,2 | ||
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Base + 400h | Parallel Data FIFO | LPT1,2,3 | ||
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Base + 400h | ECP Data FIFO | LPT1,2,3 | ||
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Base + 400h | Test FIFO | LPT1,2,3 | ||
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Base + 400h | Configuration Register A | LPT1,2,3 | ||
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Base + 401h | Configuration Register B | LPT1,2,3 | ||
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Base + 402h | Extended Control Register | LPT1,2,3 |
Base Address:
LPT1 = 378h
LPT2 = 278h
LPT3 = 3BCh
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