[previous] [next] [contents]    1149.4 instructions

Besides the three mandatory 1149.1 instructions, 1149.4 defines a fourth mandatory instruction called PROBE. The functionality of the PROBE instruction may be summarised as follows:

• The selected data register is the BS register
• Each ABM will connect its pin to the core circuitry
• AT1 and AT2 are connected to AB1 and AB2
• Connection between the analog I/O pins and AB1 / AB2 is defined according to the control register in each ABM
• Each DBM operates in transparent mode (as if SAMPLE / PRELOAD or BYPASS were the current instruction)

In relation to the three mandatory instructions common to 1149.1, the following additional 1149.4-specific rules apply:

• For BYPASS and SAMPLE / PRELOAD: i) AT1 / AT2 must be isolated from AB1 / AB2, as well as from all test voltage sources; ii) all analog function pins must be connected to the core circuit; iii) all analog function pins must be isolated from AB1 / AB2 and from all test voltage sources.
• For EXTEST: The ABMs must disconnect the pin from the core circuit.

Optional 1149.4 instructions are the same as for 1149.1 (INTEST, ID / USERCODE, RUNBIST, CLAMP and HIGHZ) and have a similar description, to which are appended the rules applying to the operating modes of the TBIC and ABMs.