Isa Super I/O Device (Isasio); Asynchronous Serial Ports; Parallel Port - Motorola MVME2700 Series Installation And Use Manual

Functional Description

ISA Super I/O Device (ISASIO)

3

Asynchronous Serial Ports

Parallel Port

3-10
The MVME2700 uses a PC87308 ISASIO chip from National
Semiconductor to implement certain segments of the P2 and front-panel
I/O:
Two asynchronous serial ports (COM1 and COM2) via P2 and
transition module
Parallel port via P2 and transition module:
– Centronics printer port in MVME712M-compatible models
– IEEE1284 bidirectional parallel port in MVME761-compatible
models
Floppy disk drive support via drive/power connector J3
Keyboard and mouse interface via circular DIN connectors J5 and
J7
The two asynchronous ports provided by the ISASIO device employ TTL-
level signals that are buffered through EIA-232-D drivers and receivers
and routed to the P2 connector.
Hardware initializes the two serial ports as COM1 and COM2 with ISA
I/O base addresses of $3F8 and $2F8 respectively. This default
configuration also assigns COM1 to PIB (PCI/ISA Bridge Controller)
interrupt request line IRQ4 and COM2 to line IRQ3. To change the default
configuration, reprogram the ISASIO device. For detailed programming
information, refer to the PCI and ISA bus discussions in the
MVME2600/2700 Series Programmer's Reference Guide and to the
vendor documentation for the ISASIO device.
The parallel port is a Centronics printer interface in MVME712M-
compatible models, and a full IEEE1284 bidirectional parallel port in
MVME761-compatible models. Both versions are implemented with the
ISASIO device. All parallel I/O interface signals are routed to P2 through
series damping resistors.
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