Level-sensitive scan design
 | This article relies on a single source. (March 2022) |
Within the field of electronics Level-sensitive scan design (LSSD) is part of an integrated circuit manufacturing test process. It is a DFT scan design method 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.[1]
____ | | 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 used as a second system latch reduces the silicon overhead.[1]
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[edit]- 1 2 This article is based on material taken from Level-sensitive+scan+design at the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.