TEST MODE DECODER
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Sep-02
Avraham Ganor: AUTHOR [+2]
Integrated circuits (KS) can comprise test cir- cuitry. Usually, a test mode is communicated to the IC by a number a dedicated pins used for testing purpose only. While the functionality of ICs becomes more and more complex, the number of available pins is limited. Testing the IC through test pins is usually required only after manufacturing but not required during normal operation. There is a need to reduce the number of test pins or to provide multi-functional pins.
Developments Technical 0 M MOTOROLA
TEST MODE DECODER
by Avraham Ganor and Yoram Yeivin
functional pins which are not related to the test itself, assume predefined values; and one of the functional pins assumes any value X which is. This X-bit communicates further information related to the test to the IC.
In other words, the test operation is entered by asserting the dedicated pin TEST, and the determi- nation of a test scheme (e.g., groups 1-3) is entered by functional pins.
For example, there can be five different test con- figurations "MODE-I" (e.g., a JTAG scan test), "MODE-2" (e.g., a core test, orthogonal to the scan test), "Group l", "Group 2". and "Group 3". MODE-1 and MODE-2 are exclusive and can only be invoked upon the presence of single bit patterns (0 1 0) or (1 0 l), respectively, at PIN-l, PIN-2 and PIN3. For the other tests, two different bit patterns
(e.g., (0 1 1) or (1 1 1) for "Group 1") can invoke the test, wherein the X-bit transmits the further information.
This proposal allows to use only one dedicated pin for entering several test modes instead of having dedicated pins for each test mode. Compared to prior solutions, the overall number of pins is reduced and thereby the chip area becomes smaller.
0 Motom,a. 1°C. ,999 251 September 1999
Integrated circuits (KS) can comprise test cir- cuitry. Usually, a test mode is communicated to the IC by a number a dedicated pins used for testing purpose only. While the functionality...