Computer Dictionary Online

Medical Dictionary   Law Dictionary   Legal Dictionary   Website Design

0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  g  h  i  j  k  l  m  n  o  p  q  r  s  t  u  v  w  x  y  z 


level-sensitive scan design

(circuit design) (LSSD) A kind of scan design which uses separate system and scan clocks to distinguish between normal and test mode. Latches are used in pairs, each has a normal data input, data output and clock for system operation. For test operation, the two latches form a master/slave pair with one scan input, one scan output and non-overlapping scan clocks A and B which are held low during system operation but cause the scan data to be latched when pulsed high during scan.

		  ____
		 |    |
	 Sin ----|S   |
	 A ------|>   |
		 |   Q|---+--------------- Q1
	 D1 -----|D   |   |
	 CLK1 ---|>   |	  |
		 |____|	  |    ____
			  |   |	   |
			  +---|S   |
	 B -------------------|>   |
			      |	  Q|------ Q2 / SOut
	 D2 ------------------|D   |
	 CLK2 ----------------|>   |
			      |____|


In a single latch LSSD configuration, the second latch is used only for scan operation. Allowing it to be use as a second system latch reduces the silicon overhead.

(1995-02-15)


Contact the Computer Dictionary Online  ::  Link to the Computer Dictionary Online  ::  Disclaimer for Computer Dictionary Online

Computer Dictionary Online
Copyright © 2017