Specifications

Hardware Configuration
2–14
Selection I/O Address
Primary 378h - 37Fh
Secondary 278h - 27Fh
Disable None
Table 2-9 Parallel Printer Port Address Configuration
For details about the parallel port I/O addresses and the data, status, control, EPP, and ECP port bit
definitions, refer to the parallel port section in Chapter 3.
2.7.2 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. Configure the parallel port for
the primary assignment shown in Table 2-9, unless you have added another parallel port that occupies
the primary parallel port’s I/O addresses. In that case, make the Little Board/486i’s parallel port the
secondary port.
2.7.3 Interrupts
The parallel port can be configured to generate an interrupt request upon a variety of conditions,
depending on the mode the port is in. (These are described in Chapter 3.) In most applications, the
interrupt is not used. The standard parallel port interrupts are:
! Primary port IRQ7
! Secondary port IRQ5
A jumper is used to select the parallel port interrupt. To select the interrupt, set jumper W17 as
shown in the following figure:
Figure 2-6 Parallel Port IRQ Selection (W17)
2.7.4 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/486i, select the
DMA request (DRQ) and DMA acknowledge (DACK) assignments using jumpers. You can configure
the parallel port to use either DMA channel 1 or DMA channel 3. To select a DMA channel for the
parallel port, set jumpers W18 and W19 as shown in the following figure: