Ampro Corporation LITTLE BOARD P5X - Manual (Page 42)

2–24
This section lists the pinout of the parallel port connector and describes how to configure it for its
I/O port and interrupt assignments, how to assign a DMA channel to the port when operating in
ECP mode. And programming information, including how to use the port for bi-directional I/O.
I/O Addresses and Interrupts
The parallel port functions are controlled by eight I/O ports and their associated register and
control functionality. The Little Board/P5x parallel port is assigned to the primary parallel port
address normally assigned to LPT1 and cannot be changed. You may disable the port in Setup to
free the hardware resources for other peripherals.
The parallel port can be configured to generate an interrupt request upon a variety of conditions,
depending on the mode the port is in. Assignment of an interrupt to the parallel port is optional,
and its use depends on software requirements and which mode of operation you are using. IRQ 7 is
the default parallel port IRQ assignment.
Table 2– 20 lists the parallel port addresses and IRQs.
Table 2– 20. Parallel Printer I/O Addresses and Interrupt
Selection I/O Address Interrupt
Primary 378h - 37Fh 7
Secondary 278h - 27Fh 5
Secondary 3BCh - 3BFh 7
Disable None None
ROM-BIOS Installation of Parallel Ports
Normally, the BIOS assigns the name LPT1 to the primary parallel port, and LPT2 to the secondary
parallel port (if present), and so on. However, the BIOS scans the standard addresses for parallel
ports and if it only finds a secondary port, it assigns LPT1 to that one. Therefore, if the Little
Board’s parallel port is enabled, it will be assigned LPT1 by the BIOS. If it is disabled and there is
another parallel port in your system, that port will be assigned LPT1 by the BIOS.
The ROM-BIOS scans I/O addresses for parallel ports in the following order: 3BCh, 378h, 278h.
DMA Channels
In ECP enhancement mode, the parallel port can send and receive data under control of an on-
board DMA controller. DMA channels operate with a request/acknowledge hardware handshake
protocol between an internal DMA controller and the parallel port logic. On the Little Board/P5x,
select a DMA channel in Setup. You can configure the parallel port to use either DMA channel 1 or
DMA channel 3.
If you will not be using DMA with the parallel port, leave it disabled. This makes the DMA channel
available to other peripherals installed on the expansion buses.