Editing Built-in self-test (section)

===Electronics===

====Integrated circuit manufacturing====

Built-In-Self-Test is used to make faster, less-expensive [[integrated circuit]] manufacturing tests. The IC has a function that verifies all or a portion of the internal functionality of the IC.  In some cases, this is valuable to customers, as well.  For example, a BIST mechanism is provided in advanced [[fieldbus]] systems to verify functionality.  At a high level this can be viewed similar to the PC [[BIOS]]'s [[power-on self-test]] (POST) that performs a self-test of the [[RAM]] and buses on power-up.

====Computers====

The typical personal computer tests itself at start-up because it's a very complex piece of machinery.  Since it includes a computer, a computerized self-test was an obvious, inexpensive feature. Most modern computers, including [[embedded system]]s, have self-tests of their computer, memory and software.

====Unattended machinery====

Unattended machinery performs self-tests to discover whether it needs maintenance or repair.  Typical tests are for temperature, humidity, bad communications, burglars, or a bad [[power supply]].  For example, power systems or batteries are often under stress, and can easily overheat or fail.  So, they are often tested.

Often the communication test is a critical item in a remote system. One of the most common unattended system is the telephone concentrator box.  This contains complex electronics to accumulate telephone lines or data and route it to a central switch.   Telephone concentrators test for communications continuously, by verifying the presence of periodic data patterns called frames (See [[SONET]]).  Frames repeat about 8,000 times per second.  

Remote systems often have tests to [[loop back]] the communications locally, to test transmitter and receiver, and remotely, to test the communication link without using the computer or software at the remote unit.  Where electronic loop-backs are absent, the software usually provides the facility.  For example, [[Internet Protocol|IP]] defines a local address which is a software loopback (IP-Address 127.0.0.1, usually locally mapped to name "localhost").  

Many remote systems have automatic reset features to restart their remote computers.  These can be triggered by lack of communications, improper software operation or other critical events.  Satellites have automatic reset, and add automatic restart systems for power and [[attitude control]], as well.