This month’s tip will discuss Port Technology. I will provide some detail in this month's tip on what computer ports enable us to do and how we can determine information and how to ensure success when using these devices.

Serial, Parallel and USB ports are used for purposes of transmitting data in various forms. Computers are equipped with numerous different technologies and commonly it can be confusing to determine what technology is the most appropriate and viable for supporting our data needs. Some of these needs are to send data via a fax machine or to a printer. In migration needs, software programs use a computer port to send data to another machine.

With Port technology, we are describing how moving date across a hardware medium can be accomplished. The following hardware shows how these are controlled and how they can be classified by speed, ease of use and availability. These port directions for use are controlled in the BIOS of the computer and can be configured with certain features and functions. Commonly the OS will be able to show information in the device manager that can provide information on how the device is configured.

Serial:
This is the oldest technology that uses 9 pins and will transfer close to 10KBS of data using one line of movement of data along with control lines that direct data to flow that can be bi-directional.

Okay, in laymen's terms: This would be equivalent to sending cars into traffic and only one road can be used, no turns allowed. The technology was written when limited single direction data was being transmitted. A wiring diagram is included that shows how serial technology is configured. The serial ports were mainly used for external modems and functions like a phone line across one wire. External modems were the main use for this technology and early generation computers (com 1,2,3,4 ports) were manufactured with these ports.

Network Cable Pinouts - RS-232
RS-232 Serial

Male DB9 serial connector viewed from front. Reverse for female connector or back view of male connector.

9-Pin DB9 Assignments

1	DCD	Data carrier (line signal) detect
2	RXD	Receive data
3	TXD	Transmitted data
4	DTR	Data terminal ready
5	GND	(Signal) ground
6	DSR	Data set ready
7	RTS	Ready/request to send
8	CTS	Clear to send
9	RI	Ring indicator

Male DB9 serial connector viewed from front. Reverse for female connector or back view of male connector.

25-Pin DB25 Assignments Parallel

1		Shield - chassis/frame protective ground
2	TXD	Transmitted data
3	RXD	Receive data
4	RTS	Ready/request to send
5	CTS	Clear to send
6	DSR	Data set ready
7	GND	(Signal) ground
8	DCD	Data carrier (line signal) detect
9		Reserved for testing - positive voltage
10		Reserved for testing - negative voltage
11		Unassigned
12	SCF	Secondary received carrier (line signal) detect
13	SCB	Secondary clear to send
14	SBA	Secondary transmitted data
15	DB	Transmission signal element timing (clock)
16	SBB	Secondary received data
17	DD	Receiver signal element timing (clock)
18		Unassigned
19	SCA	Secondary request to send
20	DTR	Data terminal ready
21	CG	Signal quality detector
22	RI	Ring indicator
23	CH/CI	Data signal rate selector
24	DA	External transmit signal element timing (clock)
25		Test mode

 

Parallel:
The next generation of data needs required transferring data through LPT ports to a printer. Parallel (LPT) ports were generated to facilitate print documents improving the process from serial technology. Parallel ports generate speeds of 100KBS and reflect transfers 10x's faster then serial speeds.

Parallel ports use a series of lines along 15 channels, with 25 pins, which use direct lines to determine data flow. Since we have 25 pins and can move data on 15 of these channels, it is significantly faster then serial technology. See Diagram above. So again, in laymen's terms, now we have much larger roads that have the ability to travel in either direction, (which is not required) but still no turns are allowed and no formal rules on how or when to travel.

Parallel is older technology developed by IBM for X86 systems but with no standards and ambiguous to most devices. IBM developed and loosely specified the characteristics of the parallel port where no standardized protocol was established. As a result many companies were able to develop their own drivers that may or may not work with other devices. This became a significant problem. As printers became more popular with more manufacturers, more devices used the BIOS manufacturers to have naming conventions that conflict or lock out the hardware port. The driver could be written to lock up the device even with out the device present. Other devices need to break this dependency to use this port technology. When this dependency is in place the port appears unresponsive, when actually it is locked up from being able to use another device until this dependency is broken. If the device is unresponsive, commonly we can find and remove printers and print drivers to allow other devices to use this port. Another common problem can be the port set-up in the Bios as described below.

Quick Starting Parallel
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http://www.lpt.com/Downloads/downloads.htm#Download%20Library%20-%20Useful%20Software%20Utilities

Parallel operates by testing each of the standard addresses in your
system where parallel ports might be found and gathering a broad
assortment of useful information about the specific port behavior.
Parallel tests the ports and then produces a compact display which
is convenient and easy to read. You may need to refer to these
instructions or the built-in reference screen a few times until you
learn what the various columns of information mean.

How to use Parallel:

Step 1	Disconnect any attached parallel port peripherals such as printers, LAN adapters, disks, CDROMs, etc
Step 2	Run PARALLEL from the DOS command line (not in Windows)
Step 3	Read the display as described below

Parallel will display five columns of information containing one or
more lines about each port. The columns are:

Port Type The parallel port's IO capabilities. Types are:

No Port	No port is exists at the address
4 bit	A "unidirectional" port
8 bit	A "bidirectional" port
EPP	An Enhanced Parallel Port
ECP	An Extended Capabilities Port

 

Address	IO Base Address of the port (3BC, 378, 278)
IRQ	Interrupt level associated with the port (5 or 7)
BIOS	Name Logical device name of the port (LPT1, LPT2, LPT3)
Notes	A wide assortment of comments, warnings, and miscellaneous additional information
Port Strangeness Factor	On a single line, after the columnar display, Strangeness Parallel ports a magic number called the Factor

This is simply the total number of strange or unusual properties that
Parallel has found when examining your configuration. If your ports are considered strange by Parallel, you might want to take some action to correct the situation, or at least appreciate the peculiarity. The Port Strangeness is not reported if your configuration is boring.

Some troubleshooting for Port usage:
For migrations that appear to have stalled out: If there is no connectivity and the port is set up for simplex operation in the Bios (outbound only ) the port will have to be reconfigured. What the labeled "names" for simplex are varies from BIOS vendor to vendor. Generally, BIOS manufacturers get ECP and EPP naming correct. Standard, Common and other names can be used for 4bit and 8bit configurations. Generally these setups work but then when they don't, steps will have to take place in the Bios to reconfigure these to work.

The Detto Migration required configurations that work are:

4 bit	A "unidirectional" port
8 bit	A "bidirectional" port
EPP	An Enhanced Parallel Port
ECP	An Extended Capabilities Port

 

USB- Universal Serial Bus
Definition: USB is a high-performance networking standard based on serial bus architecture. Most new computers and associated peripheral devices like printers and scanners support USB. USB hubs for file and printer sharing also exist. USB technology can use daisy chain devices to improve versatility of the computer and enhance use of technology across different equipment. Speed enhancements have greatly improved performance with USB 1 generating speeds at 14 megBit/sec and USB 2.0 attaining speeds of 480 megBit/sec.

Parallel technology had speed limitations with 24 pins that allowed other faster technology to become popular. The really good news is that most new technologies carry industry standards to ensure compatibility for using the port.

USB technology was developed and adopted with standards that allowed software development to build on core technology. Other devices that used USB could be predicted to act in a certain manner and other devices could co-exist. In laymen's terms, we now had a transportation infrastructure that included traffic signals, turning lanes, intersections, now able to move in a more efficient, organized standard to drive data at a higher rate of speed.

Standard USB also has some good features that will return with loop back information, describing what device it finds attached to the system. The OS will then access a database to determine what kind of device this is and having detected the device will associated the device with software. If no software drivers are found for the device the device manager will then ask the user to locate it. If the user cannot suggest a location for the required software driver the OS will mark the device as offline (or as some would say the device is "bang"ed out). This will usually require some additional intervention to resolve the problem.

Device conflicts can occur due to plug and play algorithms and can usually be resolved by unplugging all devices and then plugging them back in after new USB hardware is installed.