GLOSSARY of Printed Circuits

       U

Index to terms on this page:

U   UAV   UBGA   UDF   UEFI   uF   UL  
Ultra-Fine Pitch Technology   ULVDS  
unsaturated logic   unstuffed   US-ASCII  

U — Stands for micro, as in mirco-electronic or micro-processor. U is used for its resemblance to the Greek lower-case letter mu, μ, a symbol for micro. Because micro-processors are integrated circuits, U is used as the alpha character prefix in a reference designator which gives a name to an integrated circuit component in a schematic or on a PCB (Eg. U8). "IC" is also used for this, depending on the electronic circuit designer's personal preference (Eg. IC8).

↑  Page Index

UAV — Unmanned Airial Vehicle. The UAV is an acronym for Unmanned Aerial Vehicle, which is an aircraft with no pilot on board. UAVs can be remote controlled aircraft (e.g. flown by a pilot at a ground control station) or can fly autonomously based on pre-programmed flight plans or more complex dynamic automation systems. The UAV.

↑  Page Index

UBGA — Ultra FBGA, that is Ultra Fine-line Ball Grid Area. UBGA is used by Altera to designate BGAs with a ball pitch of 0.8mm.

↑  Page Index

UDF — (Universal Disc Format). This format is only supported by Windows Me and later versions and should be selected when creating video DVDs. The DVD Forum's DVD-VR format uses UDF 2.00 for DVD-R, DVD-RW and DVD-RAM. Philips' DVD+VR format uses UDF 1.02 with an ISO 9660 bridge for DVD+R and DVD+RW.

↑  Page Index

UEFI —  [Computer Systems Administration]  Unified Extensible Firmware Interface. BIOS (firmware) and UEFI (software) are two interfaces for computers to start the operating system and peripherals .

BIOS vs UEFI excepted from The Windows Club. "UEFI vs BIOS: What Is the Difference between BIOS and UEFI?" The Windows Club, The Windows Club, 10 Dec. 2021, www.thewindowsclub.com/difference-between-bios-and-uefi.

While they are both used for starting the computer, they are NOT the same. BIOS is firmware that uses the Master Boot Record (MBR) to save information about the hard drive data while UEFI is software that uses the GUID Partition Table (GPT) .

UEFI was originally developed in 2007 as a standard for modern interfaces. This platform supports a wide variety of modern hardware platforms. This is the newer and more advanced firmware interface that aims to correct the technical shortcomings of BIOS. Similar to BIOS, it also serves as a bridge, connecting a computer's operating system to its firmware. UEFI comes with a number of features and advantages that cannot be obtained through the legacy BIOS. This technology will eventually replace the BIOS entirely.

In UEFI, the .efi file (not a firmware file such as BIOS uses) stores all startup information, and it is located on the EFI System Partition on the hard drive. You’ll find the bootloader on the same partition. The most important thing to note here is that UEFI bypasses the BIOS Power On Self Test (POST) so that the operating system can boot directly. Unlike BIOS, it does not have restrictions on size, so more components can be initialized simultaneously.

BIOS only works in 16 bits and therefore it cannot address more than 1MB of space. As a consequence, it can only initialize one device at a time and the booting might take longer.

In contrast, UEFI operates in 64-bit mode, meaning it has higher addressable memory and thus it makes the booting process faster. Furthermore, UEFI supports networking, so you can troubleshoot remotely even without installing an operating system. As a result, most motherboard manufacturers find it to be a much better choice in most cases. For this reason, it has gained popularity recently.

The next difference between the two programs is that BIOS stores bootloader data in the Master Boot Record (MBR). The MBR is located in the first sector of the disk, so it can be easily corrupted, which would make the operating system unresponsive.

UEFI, on the other hand, makes use of the GUID Partition Table, which performs cyclic redundancy checks to identify any corruption issue. Thus, it creates a more robust boot environment that can be easily recovered. It is capable of supporting more than four primary partitions.

↑  Page Index

uF — microfarad. One millionth of a Farad. (For Farad, see a good dictionary of electronics such as [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999] .)

↑  Page Index

UL — Underwriter's Laboratories, Inc., a corporation supported by some underwriters for the purpose of establishing safety standards on types of equipment or components.

↑  Page Index

Ultra-Fine Pitch Technology — A surface-mount assembly technology with component terminations on centers less than or equal to 0.40 mm [15.7 mil].

↑  Page Index

ULVDS — Ultra Low Voltage Differential Signaling

↑  Page Index

unsaturated logic — A form of logic containing transistors operated outside the region of saturation , which makes for very fast switching.  An example is emitter-coupled logic ( ECL ).  (For other definitions and examples see [Graf, Rudolf F. Modern Dictionary of Electronics. Newnes, 1999].

↑  Page Index

unstuffed — Slang [PCB Manufacturing] Not populated.

↑  Page Index

US-ASCII — The 7-bit (using character codes 0-127) version of ASCII, which preceded (and is the basis for) 8-bit versions such as Latin-1, MacASCII and later, even larger coded character sets such as Unicode.

↑  Page Index