HITR - Common Interfaces - Parallel Port Controller
First Edition (October 1990)
IEEE 1284 – Updating the PC Parallel Port
National Instruments - Application Note 062
Interfacing Articles by Craig Peacock
When my Parallel to CF adapter arrives, I can test it on a Type 4 (95A ExpressPrint) port.
Update: Attempts to install on a Model 90's Type 3 parallel port blue screened an NT4 SP6a so bad I couldn't even get to [UN] Safe Mode.
Parallel Port Information System
version 1.45, Jay Lowe and Don Schuman 27 Oct 1994
95A Parallel Ports
95A Parallel Ports
The 95A planar has 2 parallel ports:
If you experience a problem with a non-IBM device when
attaching it to either the parallel port, you might need
to go to the Change configuration screen of the system
programs and set the port DMA (direct memory access)
arbitration level to "Disabled."
ExpressPrint Parallel Port supports transfer rates at up to 2 MB/s. Using vendor supplied multiplexer (i.e. F/MUX) and software, users can attach up to four supported printers and output 300 DPI complex graphics at the rated speed of the printer and still have capacity left over. Compared to a direct LAN attachment, where data is sent over the LAN twice before being printed, the busmaster ExpressPrint Parallel Port not only reduces the load on the server processor, but prevents the LAN from being flooded with unnecessary printer traffic.
The Hunt for Red ExpressPrint
Subject: Just what is ExpressPrint and how do I use it?
The lone existing F/Mux is all I know to be in existence. I'm not sure if Warp Nine Engineering will ever produce it. Now that USB is out, there is less reason than ever to do so. For more info on the F/Mux, go HERE.
Parallel Resistor Networks on 95A
Bourns 4816P-001 -330 (isolated 33 ohm) and 4816P-002 -472 (bussed 4.7K ohm) for each parallel port. Datasheet for the 4800P family HERE.
Parallel Port Address Assignments
* Parallel_x has been shortened to Par_x so the table fits.
Updated W95 Printer Driver
Found this on Russ Wright's Cannon
PRNT5UPD.EXE contains the latest
LPT.VXD driver file.
Windows 95 Printing Extended Capabilities Port Support
(Ed. Applies ONLY to LPT A on 95A systems!)
An ECP provides high-speed printing, and support for ECP and ECP devices is included in Windows 95. If you have an ECP, you can connect either ECP or non-ECP devices to the port. In either case, using an ECP will improve I/O performance, although ECP devices will show the greatest I/O gains. An ECP can be configured in five different ways (defined in the port’s Resources properties), as shown in the following list.
Basic *.inf Configuration(s) Description
0 Standard I/O ranges for LPT ports only
To enable ECP support in Windows 95
1. Consult your computer (or add-in card) manual to
determine the IRQ and DMA settings selected for each of
the ECP ports you want to use. You’ll need this
information to enable ECP support.
Direct Cable Connection
I've used DCC under W95 to hook up a 9533 to a 77s. A 76s to a 77s. Go to the very detailed Connect Pages at Kime.Net to find out how! Sure beats the hell out of SneakerNet for 70+MB!
DMA Parallel Port (Uncut!)
With apologies to "The Micro Channel Architecture Handbook" ISBN 0-13-583493-2, pages 99-100. Spelling mistakes are probably mine.
"A practical application of Micro Channel
technology that breaks the microprocessor bottleneck in
printing is making the printer port into a DMA that uses
a Direct Memory Access controller to move the data.
During a print job, the DMA printer port would briefly
take control of the bus, shuttle the data across, and
step out of the way.
The load on the bus itself would
immediately be reduced by this technology, but that's
only of the tiniest benefit to system performance. This
sort of advanced printer port trims the overhead on the
bus because it requires only the equivalent of 68,000
characters per second in bus time to support the same
100,000 characters per second data rate. Fewer
instructions than characters are required because a
16-bit DMA bus master would be able to move two
characters at a time to the printer port instead of the
single character permitted by most printer ports in
classic bus systems. (Overhead mitigates the two-to-one
theoretical advantage of the double-width bus.) Of
course, this increase in bus width and consequent
bandwidth saving is only an implementation issue more
significant with multitasking.
The important increase in performance to
the single-tasking system comes from savings in
microprocessor usage. Nearly all of the millions of
instructions per second used in the classic bus scenario
could be freed up from the microprocessor by the bus
master DMA printer port. The microprocessor would need
to do nothing but spend a few thousand cycles to set up
the DMA transfer, rather than continuously churning
through millions of instructions every second. The DMA
controller itself would do all the dirty work. The
instructions it races through would not impact system
performance at all.
All the time that the adapter and DMA
controller are not putting data on the bus most of the
time, considering that less than 1/10th (in truth,
closer to 1/20th) of the bus bandwidth is used for
actual transfer of characters per task. Instead of being
fully loaded and unable to perform other tasks with any
speed at all, the system with a DMA printer port would
have more than 90 percent of it's potential available
while the printer is running full speed. If the
microprocessor has it's own cache memory, the impact on
system performance would be even less, potentially zero.
The economics of adding a DMA printer
port to a high-performance Micro Channel computer are
astounding. The parts required to make a DMA printer
port are insignificant compared to the cost of an
80386-based computer. As a result, in practical terms a
DMA printer adapter could buy back most of that system's
performance for less than one percent of the total
system cost. In effect, DMA buys you the performance of
another 80386-based computer for practically nothing.
A true bus master printer port would save
more bus cycles and might be easily justified in a
multitasking or multiuser system where bus cycles are at
a premium. Remember that as earlier stated I/O transfers
can take 5 or perhaps 10 percent of the bus bandwidth per task. This means that
5 or 10 tasks might consume a sizeable portion of bus
bandwidth at the expense of performance overall. In the
single-tasking system, however, the delays introduced by
the processor-dependent I/O adapters can be
cost-effectively overcome by DMA.
Checking for Parallel DMA Use
Q. I know that the 56/57/76/77/85/90/95 systems use serial and parallel ports capable of high-speed DMA transfers, but how do I know if my system is set up to use DMA?
A. Simple. Start the System Program (either from the System Partition on your hard disk drive, or the Refdisk), and look at the Arbitration Level for the serial and parallel ports. The parallel port should be set to Shared 7, and the serial port should be set to Shared 4 for Transmit Arb Level, and Shared 3 for Receive Arb Level. If your system has two DMA serial ports, the second serial port should be set to Shared 6 for Transmit Arb Level, and Shared 5 for Receive Arb Level. These are the defaults. If the ports are set this way, they are using DMA.
Two Parallel Ports under W98SE
How do I ensure both my parallel ports are enabled on a 95A?
Dr. Jim Shorney (on sabbatical)
I had to then change the ECP port @ manually
under the resources tab to 278-27A. (No more conflicts).
Both the printer and video camera are working fine.
Printer on plain LPT port and camera on LPT2 (ECP) with
> Peter, is there a patch that allows the reconfiguration of the parallel port to bidirectional?
Err ... PS/2 sysboard LPT are bidirectional by nature.
There are 3 registers used on LPT ports:
The I/O port address for LPT1 is usually
03BCh on PS/2, the control register is then 03BEh. (You
can determine the address with reading the bytes at
0000:0408 and 0000:0409 in the Bios address space - the
LSB is first, it will read BC 03).
If you set bit 5 (direction) of the
control register to 1 you can read from the bytes
present at the data-register. To permanently read from
the LPT-port you need to set the bit 0 (strobe) to 1 you
get the bit pattern changes on the port. I use that for
the little program that reads the CP codes from another
A proper handshake signaling between two
computers using the bidirectional mode will most likely
work over reading the BUSY lines from one computer to
the ACK signal on the other ... you need to read the
status of the two lines to determine, which of the two
is the sender and which receives data. This is a bit
tricky ... but some other software does that already and
uses this feature.
The PS/2 parallel port is a great device
to be used as e.g. input from a Analog-to-Digital
converter (however: only 8 bit resolution). For many
simple purposes this is truly great. I used the
parallel port to control the functions of my AKAI
tape-machine ... or used it for some other weird
The system board provides two 25-pin
D-shell connectors to the parallel port controllers on
the system board. The drivers to the data lines can
source up to 15 milliamps and sink up to 24
Parallel Port Connector Pinout
* Data parity is a function of parallel port A
Parallel Port Addresses vs. Modes
Compatible is the
old-styled unidirectional printer port
I have installed an ECP Printer Port under
"Add New Hardware". Go to the ECP Port's Resources and
select the correct address and DMA Channel. It appears
that DMA Channel 1 is used by DMA Arbitration Level 1.
Am unsure if that's true, but it still works. I don't
have a parallel port device yet to verify this other
than my digital camera.
ADF Settings for Parallel Ports
Not all systems support these settings, nor will they be in the same order.
Parallel Port x
Parallel Port x DMA
Parallel Port x SCB I/O