IBM 6278 Personal Computer User Manual


 
Chapter 2. System board features
The default setting for the serial port is COM1.
Parallel port
Integrated in the system board is support for extended capabilities port (ECP), enhanced parallel port
(EPP), and standard parallel port (SPP) modes. The modes of operation are selected through the
Configuration/Setup Utility program with the default mode set to ECP. The ECP and EPP modes are
compliant with IEEE 1284.
The following figure shows the parallel port assignments used in the configuration.
The default setting for the parallel port is Parallel 1.
The system board has one connector for the parallel port. For information on the connector pin
assignments, see “Parallel port connector” on page 34.
Keyboard and mouse ports
The keyboard and mouse subsystem is controlled by a general purpose 8-bit microcontroller; it is
compatible with 8042AH. The controller consists of 256 bytes of data memory and 2 KB of read-only
memory (ROM).
The controller has two logical devices: one controls the keyboard and the other controls the mouse. The
keyboard has two fixed I/O addresses and a fixed IRQ line and can operate without the mouse. The
mouse cannot operate without the keyboard because, although it has a fixed IRQ line, the mouse relies on
the addresses of the keyboard for operation. For the keyboard and mouse interfaces, no resource
assignments are given in the system memory addresses or DMA channels. For information on the
resource assignments, see “Input/output address map” on page 36 and Figure 36 on page 40 (for IRQ
assignments).
The system board has one connector for the keyboard port and one connector for the mouse port. For
information on the connector pin assignments, see “Mouse and keyboard port connectors” on page 33.
Figure 5. Serial port assignments
Port assignment Address range (hex) IRQ level
Serial 1 03F8–03FF IRQ4
Serial 2 02F8–02FF IRQ3
Serial 3 03E8–03FF IRQ4
Serial 4 02E8–02FF IRQ3
Figure 6. Parallel port assignments
Port assignment Address range (hex) IRQ level
Parallel 1 03BC–03BE IRQ7
Parallel 2 0378–037F IRQ5
Parallel 3 0278–027F IRQ5
Chapter 2. System board features 11