Pci Bus; Parallel Interface - NEC PowerMate V486 Series Service Manual

PCI Bus

The industry-standard PCI bus is a highly-integrated input/output (I/O) interface that offers
the highest performance local bus available for the 486-based processor. The PCI bus sup-
ports burst modes that send large chunks of data across the bus, allowing fast displays of
high-resolution images.
The high-bandwidth PCI local bus eliminates data bottlenecks found in traditional systems,
maintains maximum performance at high clock speeds, and provides a clear upgrade path
to future technologies.
The PCI bus slot is used in conjunction with an ISA bus slot. This feature allows a PCI bus
option board full access to the ISA bus. For example, the PCI bus option board may utilize
the parallel port via the ISA bus, or use the ISA bus REFRESH signal. Use of the ISA bus
is optional, as the PCI bus has all signals needed to fully support a PCI bus option board.

PARALLEL INTERFACE

The system has a 25-pin parallel port on the system board. Specifications for this port con-
form to the IBM-PC standards.
The BIOS has automatic ISA printer port sensing. If the BIOS detects an ISA printer port
mapped to the same address, the built-in printer port is disabled. The BIOS also sets the
first parallel interface port it finds as LPT1 and the second port it finds as LPT2. The inter-
rupt is set to IRQ5 via the Setup and jumper settings.
Interrupt levels for the parallel port are given in Table Section 1-13. Software selectable
base addresses are 3BCh, 378h, and 278h.
Parallel interface signals are output through the system board's 25-pin, D-subconnector.
The connector is located at the rear of the system unit. Pin locations for the parallel inter-
face connector are shown in Appendix A.
Table Section 1-13 Parallel Port Addressing and Interrupts
Starting I/O Address
378
278
3BC
*Default for parallel port
NOTE: Interrupts used for the built-in parallel
port are not available for ISA parallel ports.
Interrupt Level
IRQ05
IRQ05
IRQ05
Technical Information
Port
LPT1
LPT1 or LPT2
LPT1 or LPT2
1-15