Cell-Efficient LSSD Asynchronous Edge-Triggered Data Latch and Recognizer
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
A common problem in any LSSD design is to synchronize external asynchronous signals to the internal clocks. This article describes a method of latching external data synchronously with the internal clocks, while complying with all LSSD testability rules. This clocking methodology allows an asynchronous signal to generate a clock to latch the data. The latching of the data is not dependent on the internal clocks of the chip (see Fig. 1). It should be stressed that this method of latching data is completely LSSD compatible. The Sample Pulse is used when operating the chip in normal mode; this represents the Asynchronous External Clock. The System 3 Clock is used by all of the Asynchronous Data Latches on the chip when generating LSSD test patterns. Asynchronous data is latched into Buffer 1 on the edge of Sample Pulse.