Quatech RS-232 - Manual (Page 10)

4 Address Map and Special Registers
This chapter explains how the eight UARTs and special registers
are addressed, as well as the layout of those registers. This material will
be of interest to programmers writing driver software for the
ESC(LP)-100.
4.1 Base Address and Interrupt Level (IRQ)
The base address and IRQ used by the ESC(LP)-100 are determined
by the BIOS or operating system. Each serial port uses 8 consecutive I/O
locations. The eight ports reside in a single block of I/O space in eight
byte increments, for a total of 64 contiguous bytes, as shown in Figure 2.
Base Address + 56 to Base Address + 63 Serial 8
Base Address + 48 to Base Address + 55 Serial 7
Base Address + 40 to Base Address + 47 Serial 6
Base Address + 32 to Base Address + 39 Serial 5
Base Address + 24 to Base Address + 31 Serial 4
Base Address + 16 to Base Address + 23 Serial 3
Base Address + 8 to Base Address + 15 Serial 2
Base Address + 0 to Base Address + 7 Serial 1
I/O Address Range Port
Figure 2 --- Port Address Map
All eight serial ports share the same IRQ. The ESC(LP)-100 signals
a hardware interrupt when any port requires service. The interrupt signal
is maintained until no port requires service. Interrupts are level-sensitive
on the PCI bus.
The base address and IRQ are automatically detected by the device
drivers Quatech supplies for various operating systems. For cases where
no device driver is available, such as for operation under DOS, Quatech
supplies the "QTPCI" DOS software utility for manually determining the
resources used. See Section 6.3.1 for details.
ESC(LP)-100 User's Manual 4