PC87307VUL National Semiconductor, PC87307VUL Datasheet - Page 111

• Manufacturer Part Number: PC87307VUL
• Description: PC87307/PC97307 Plug and Play Compatible and PC97 Compliant SuperI/O
• Manufacturer: National Semiconductor

6.0 Parallel Port (Logical Device 4)
The Parallel Port is a communications device that transfers
parallel data between the system and an external device.
Originally designed to output data to an external printer, the
use of this port has grown to include bidirectional communi-
cations, increased data rates and additional applications
(such as network adaptors).
6.1 PARALLEL PORT CONFIGURATION
The part offers a wide range of Parallel Port configurations.
It utilizes the most advanced protocols in current use, while
maintaining full backward compatibility to support existing
hardware and software. It supports two Standard Parallel
Port (SPP) modes of operation for parallel printer ports (as
found in the IBM PC-AT, PS/2 and Centronics systems),
two Enhanced Parallel Port (EPP) modes of operation, and
one Extended Capabilities Port (ECP) mode. This versatility
is achieved by user software control of the mode in which
the device functions.
The IEEE 1284 standard establishes a widely accepted
handshake and transfer protocol that ensures transfer data
integrity. This parallel interface fully supports the IEEE 1284
standard of parallel communications, in both Legacy and
Plug and Play configurations, in all modes except the EPP
revision 1.7 mode described in the next section.
6.1.1
The part supports Standard Parallel Port (SPP), Enhanced
Parallel Port (EPP) and Extended Capabilities Port (ECP)
configurations.
•
•
•
In the Standard Parallel Port (SPP) configuration, data
rates of several hundred bytes per second are
achieved. This configuration supports the following op-
eration modes:
— In SPP Compatible mode the port is write-only (for
— PP FIFO mode enhances SPP Compatible mode by
— In SPP Extended mode, the parallel port becomes a
The Enhanced Parallel Port (EPP) configuration sup-
ports two modes that offer higher bi-directional through-
put and more efficient hardware-based handling.
— The EPP revision 1.7 mode lacks a comprehensive
— EPP revision 1.9 mode offers data transfer enhance-
The Extended Capabilities Port (ECP) configuration ex-
tends the port capabilities beyond EPP modes by add-
ing a bi-directional 16-level FIFO with threshold
interrupts, for PIO and DMA data transfer, including de-
mand DMA operation. In this mode, the device becomes
data). Data transfers are software-controlled and
are accompanied by status and control handshake
signals.
the addition of an output data FIFO, and operates as
a state-machine instead of software-controlled oper-
ation.
read/write port, that can transfer a full data byte in ei-
ther direction.
handshaking scheme to ensure data transfer integ-
rity between communicating devices with dissimilar
data rates. This is the only mode that does not meet
the requirements of the IEEE 1284 standard hand-
shake and transfer protocol.
ment, while meeting the IEEE 1284 standard.
Parallel Port Operation Modes
Parallel Port (Logical Device 4)
111
6.1.2
The operation mode of the parallel port is determined by
configuration bits that are controlled by software. If ECP
mode is set upon initial system configuration, the operation
mode may also be changed during run-time.
Table 6-1 shows how to configure the parallel port for the
different operation modes.
Table 2-4 on page 26 shows how to allocate a range for the
base address of the parallel port for each mode. Parallel
port address decoding is described in Chapter 2.2.2 on
page 25.
The parallel port supports Plug and Play operation. Its inter-
rupt can be routed on one of the following ISA interrupts:
IRQ1 to IRQ15 except for IRQ 2 and 13. Its DMA signals
can be routed to one of three 8-bit ISA DMA channels. See
Section 6.5.19 on page 127.
The parallel port device is activated by setting bit 4 of the
system Function Enable Register 1 (FER1) to 1. See Sec-
tion 9.2.3 on page 173.
6.1.3
The parallel port output pins are protected against potential
damage from connecting an unpowered port to a powered-
up printer.
6.2 STANDARD PARALLEL PORT (SPP) MODES
Compatible SPP mode is a data write-only mode that out-
puts data to a parallel printer, using handshake bits, under
software control.
In SPP Extended mode, parallel data transfer is bi-direc-
tional. Table 6-12 on page 134 lists the output signals for
the standard 25-pin, D-type connector. Table 6-2 lists the
reset states for handshake output pins in this mode.
•
•
a hardware state-machine with highly efficient data
transfer control by hardware in real-time.
The part enters the ECP mode by default after reset.
The ECP configuration supports several modes that are
determined by bits 7-5 of the ECP Extended Control
Register (ECR) at offset 402h. Section 6.6 on page 128
describes these modes in detail. The ECR register is de-
scribed in Section 6.5.12 on page 124.
Configuration at System Initialization (Static) - The
parallel port operation mode is determined at initial sys-
tem configuration by bits 7-4 of the SuperI/O Parallel
Port Configuration register at index F0h of logical device
4. See Section 2.7.1 on page 37.
Configuration at System Initialization with Run-
Time Reconfiguration (Dynamic) - The parallel port
operation mode is initially ECP, but may be changed by
additional mode selection bits if bit 4 of the SuperI/O
Parallel Port Configuration register at index F0h of logi-
cal device 4 is 1, and bits 7-5 of the same register are
110 or 111.
In this case, the operation mode is determined by bits 7-
5 of the parallel port Extended Control register (ECR) at
parallel port base address + 402h and by bits 7 and 4 of
the Control2 register at second level offset 2. These reg-
isters are accessed via the internal ECP Mode Index
and Data registers at parallel port base address + 403
and parallel port base address + 404h, respectively.
Configuring Operation Modes
Output Pin Protection
www.national.com