Nuts & Volts, Joseph Carr, March 1997
It's been awhile since I've seen a book as practical as this one. Parallel Port Complete is a real keeper!


Personal Engineering and Instrumentation News, Paul Schreier, May 1997
An excellent resource for Visual Basic programmers looking to interface hardware through standard ports. Anyone designing hardware to work with a parallel port is well advised to add this book to their library.


Electronics Now, Jeff Holtzman, Aug. 1997
If you want to learn about PC-based parallel ports, then you need a copy of Jan Axelson's Parallel Port Complete. Good stuff.


Windows Developer's Journal, Feb. 1998
The book is written in a very readable style and starts off with the basics; you don't have to be a hardware guru to read it. If you think you might ever need to access a parallel port (under any operating system), this book is for you.


Bill Machrone, PC Week, July 20, 1998
If you need to do any development of parallel port devices or want to get a bit-level understanding of the port's inner workings, I strongly recommend Parallel Port Complete.


Book Description
A guide to programming, interfacing, and using the personal computer's parallel printer port. Includes circuit designs and Visual-Basic code examples, plus tips on how to get the most out of the port, including the enhanced (EPP) and extended-capabilities (ECP) ports found on most new systems. Includes disk.


Download Description
This detailed guide for programmers, developers, and computer enthusiasts shows how to get the most from parallel port in any application or project. The Visual-Basic code and circuit designs include examples that use the new enhanced (EPP) and expanded (EPC) modes.


Excerpted from Parallel Port Complete by Jan Axelson, Janet Louise Axelson. Copyright © 1997. Reprinted by permission. All rights reserved
From Chapter 11, Modes for Data Transfer: Detecting an ECP In testing a port, you might think that the first step would be to test for an SPP, and work your way up from there. But if the port is an ECP, and it happens to be in its internal SPP mode, the port will fail the PS/2 (bidirectional) test. For this reason, the TestPort routine in Listing 4-4 begins by testing for an ECP. An ECP has several additional registers. One of these, the extended control register (ECR) at base address + 402h, is useful in detecting an ECP. Microsoft's ECP document recommends a test for detecting an ECP. First, read the port's ECR at and verify that bit 0 (FIFO empty) =1 and bit 1 (FIFO full) =0. These bits should be distinct from bits 0 and 1 in the port's Control register (at base address + 2). You can verify this by toggling one of the bits in the Control register, and verifying that the corresponding bit in the ECR doesn't change. A further test is to write 34h to the ECR and read it back. Bits 0 and 1 in the ECR are read-only, so if you read 35h, you almost certainly have an ECP. If an ECP exists, you can read and set the port's internal ECP mode in bits 5, 6, and 7 of the ECR. In Listing 4-4, a combo box enables users to select an ECP mode when a port is ECP. Chapter 15 has more on reading, setting, and using the ECP's modes. From Chapter 7, Output Applications: Solid-state Relays Another way to switch power to a load is to use a solid-state relay, which offers an easy-to-use, optoisolated switch in a single package. Figure 7-7A shows an example. In a typical solid-state DC relay, applying a voltage across the control inputs causes current to flow in an LED enclosed in the package. The LED switches on a photodiode, which applies a control voltage to a MOSFET's gate, switching the MOSFET on. The result is a low resistance across the switch terminals, which effectively closes the switch and allows current to flow. Removing the control voltage turns off the LED and opens the switch. Solid-state relays are rated for use with a variety of load voltages and currents. Because the switch is optoisolated, there need be no electrical connection at all between the control signal and the circuits being switched. Solid-state relays have an on resistance of anywhere from a few ohms to several hundred ohms. Types rated for higher voltages tend to have higher on resistances. Solid-state relays also have small leakage currents, typically a microampere or so, that flow through the switch even when off. This leakage current isn't a problem in most applications. There are solid-state relays for switching AC loads as well. These provide a simple and safe way to use a logic signal to switch line voltage to a load. Inside the relay, the switch itself is usually an SCR or TRIAC. Zero-voltage switches minimize noise by switching only when the AC voltage is near zero.

FROM THE PUBLISHER