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Embedded Systems Glossary: W
Mon, 2007-11-19 16:57 - webmaster
n. A memory test that involves moving a 1 bit through a byte or word to systematically confirm each bit can hold a 1 value. All of the other bits are set to 0 during the test. See also checkerboard test. [more]
EXAMPLE: An 8-bit walking 1s test begins by writing 00000001b to the test memory location, then reading it back. If the same value was read back successfully, then 00000010b is written and confirmed via a subsequent read. Then 00000100b, 00001000b, ... , and 10000000b are each tested. If all values are read back properly, then the data bus passes the test.
n. A fail-safe mechanism that intervenes if a system stops functioning. Abbreviated WDT. A hardware timer that is periodically reset by software. If the software crashes or hangs, the watchdog timer will expire, and the entire system will be reset automatically. [more]
n. Like a breakpoint, but in the data area of memory rather than the code area. Any access to this location with the specified access type (read, write, read/write) stops execution and switches control to the debugger. Hardware support is required for realization of watchpoints. Watchpoints are not supported by all debugging tools.
n. TCP and UDP port numbers 0 through 1023, which are reserved for standardized protocols, such as FTP, telnet, HTTP, and others.
FURTHER READING: http://www.iana.org/assignments/port-numbers
N. The company that developed the VxWorks real-time operating system. Sometimes just Wind River or abbreviated WRS (such as online at http://www.wrs.com). Since its acquisition of competitor Integrated Systems (developers of pSOS) in 2000, Wind River has been the dominant player in the RTOS marketplace. In a 2002 survey of Embedded Systems Programming subscribers, about 60% of those reporting they used a commercial RTOS in the past year had used one of Wind River's products.
N. An embeddable variant of Microsoft's Windows operating systems. Abbreviated WinCE. Originally lacking real-time capabilities and still quite large (8 MiB flash, minimum), WinCE has not yet taken off in the embedded space as Microsoft had hoped (and many RTOS vendors feared).