PC87309VLJ datasheet(79/192 Pages) NSC

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Parallel Port (Logical Device 1)

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4.0

Parallel Port (Logical Device 1)

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).

4.1

PARALLEL PORT CONFIGURATION

The PC87309 Parallel Port device offers a wide range of op-

erational configurations. It utilizes the most advanced proto-

cols in current use, while maintaining full backward

compatability to support existing hardware and software. It

supports two Standard Parallel Port (SPP) modes of opera-

tion 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 soft-

ware 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.

4.1.1

Parallel Port Operation Modes

The PC87309 parallel port supports Standard Parallel Port

(SPP), Enhanced Parallel Port (EPP) and Extended Capa-

bilities 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

data). Data transfers are software-controlled and are

accompanied by status and control handshake sig-

nals.

— PP FIFO mode enhances SPP Compatible mode by

the addition of an output data FIFO, and operation

as a state-machine operation instead of software-

controlled operation.

— In SPP Extended mode, the parallel port becomes a

read/write port, that can transfer a full data byte in ei-

ther direction.

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

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.

— EPP revision 1.9 mode offers data transfer enhance-

ment, while meeting the IEEE 1284 standard.

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

a hardware state-machine with highly efficient data

transfer control by hardware in real-time.

The PC87309 enters ECP mode by default after reset.

The ECP configuration supports several modes that are

determined by bits 7-5 of the ECP Extended Control

ECP MODE DESCRIPTIONS" on page 95 describes

these modes in detail. The ECR register is described in

Section 4.5.12 "Extended Control Register (ECR)" on

page 91.

4.1.2

Configuring Operation Modes

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.

Configuration at System Initialization (Static) - The

parallel port operation mode is determined at initial sys-

tem configuration by bits 7-5 of the SuperI/O Parallel

Port Configuration register at index F0h

Configuration at System Initialization with Run-

Time Reconfiguration (Dynamic) - When ECP mode

is selected as the static all other operational modes may

be run from this state. 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 sec-

ond level offset 2. These registers are accessed via the

internal ECP Mode Index and Data registers at parallel

port base address + 403 and parallel port base address

+ 404h, respectively.

TABLE 4-1

"Parallel Port Mode Selection" on page 80

shows how to configure the parallel port for the different op-

eration modes.

TABLE 2-3 "Parallel Port Address Range Allocation" on

page 21 shows how to allocate a range for the base address

of the parallel port for each mode. Parallel port address de-

coding is described in Section 2.2.2 "Address Decoding" on

page 20.

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 4.5.19 "PP Confg0 Register" on page 94.

The parallel port device is activated by setting bit 4 of the

system Function Enable Register 1 (FER1) to 1. See Sec-

tion 7.2.3 "Function Enable Register 1 (FER1)" on page

155.

4.1.3

Output Pin Protection

The parallel port output pins are protected against potential

damage from connecting an unpowered port to a powered-

up printer.

4.2

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 4-12 "Parallel Port Pin Out" on page 101 lists

the output signals for the standard 25-pin, D-type connec-

tor. TABLE 4-2 "Parallel Port Reset States" on page 80 lists

the reset states for handshake output pins in this mode.

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