Specifications

33
EPC-30 Hardware Reference
Page 41
The COMA serial port is provided by the first UART in the
Intel386 EX processor, and is located in the I/O address range
0x3F8-0x3FF. COMA serial port interrupts are signaled using the
interrupt IRQ4 within the processor. Disabling this COMA port
routes its IRQ4 signal to an external pin on the 386EX, which
makes it available for the SMC COMB and COMC ports.
Connection to COMA is made either through a standard male DB-9
connector or via a standard 10-pin header configured to match
readily available pig-tails. The DB-9 is typically installed. It is not
possible to populate both the DB-9 connector and the 10-pin header.
The COMB serial port is provided by the first UART in the Super
I/O chip, and can be located at the base I/O addresses 3F8, 2F8,
3E8, or 2E8. COMB serial port interrupts are signaled using either
IRQ3, IRQ4, IRQ5 or IRQ9, selected by a resistor. Connection to
COMB is made via a standard 10-pin header configured to match
readily available pig-tails.
The COMC serial port is provided by the second UART in the
Super I/O chip, and can be located at the base I/O addresses 3F8,
2F8, 3E8, or 2E8. COMC serial port interrupts are signaled using
the interrupt IRQ3, IRQ4, IRQ5 or IRQ9, selected by a resistor.
Connection to COMC is made via a standard 10-pin header
configured to match readily available pig-tails.
Note that the arrangement of IRQs allows the Super I/O ports to be
mapped as COM1 (instead of COM4) if the 386EX internal UARTs
are disabled. This may be desired if 386EX port pins that are used
for the serial ports are needed for other uses, such as DMA. Not all
IRQ options are available to all addresses. See Table 3-2 for a
comprehensive list of IRQ and Base Address configurations.
Base Address IRQ Options
COMB 3F8 IRQ 4,5,9
2F8 IRQ 3,5,9
3E8 IRQ 4,5,9
2E8 IRQ 3,5,9
COMC 3F8 IRQ 4,5,9
2F8 IRQ 3,5,9
3E8 IRQ 4,5,9