Specifications

Little Board/P5i Technical Manual
2–10
All ports support software selectable standard baud rates up to 115.2.2K bits/second, 5-8 data bits, and 1,
1.5, or 2 stop bits. Note that the IEEE RS232C specification limits the serial port to 19.2K bits/second
on cables up to 50 feet in length.
RS-485 Adapter Power (W1)
Install a jumper on W8 if you attach an Ampro RS485 Adapter to Serial 4 (J13). It supplies +5 volt
power to the adapter through J13-11.
2.5.1 I/O Addresses
The serial ports appear at the standard port addresses as shown in Table 2-6. These are fixed assignments
and cannot be changed. Each serial port, however, can be independently disabled using the SETUP
function, freeing its I/O addresses for use by other devices installed on the PC/104 and PCI expansion
buses. For information about serial port configuration using SETUP, see Chapter 3.
Table 2–6 Serial Port I/O Addresses and Interrupts
Port I/O Address Interrupt
Serial 1 3F8h - 3FFh 4
Serial 2 2F8h - 2FFh 3
Serial 3 3E8h - 3EFh 4 or 12
Serial 4 2E8h - 2EFh 3 or 10
2.5.2 Interrupt Assignments
As shown in Table 2-6, Interrupt 4 (IRQ4) is assigned to Serial 1 and Interrupt 3 (IRQ3) to Serial 2.
These assignments can be disabled, but they cannot be changed. Serial 3 and Serial 4 can share these
same interrupts, using a “wired-or” configuration, they can use independent IRQs, or they can be
disabled and use no interrupt at all. Jumper options are provided to independently select the wired-or
configuration or independent interrupts for Serial 3 and Serial 4.
Figure 2–2 Serial 3 Interrupt Configuration (W4, W6)