[previous] [next] [contents]    Functional description of a basic 1149.4 component

This section presents a summary functional specification for a basic 1149.4 component, shown in figure 1, which is to be implemented with the objective of supporting “hands-on” mixed-signal test experiments based on this IEEE standard.

Figure 1: Simplified representation of the basic 1149.4 demo component.

Figure 1 highlights the following main features:

  • Four functional pins (2 analog, 2 digital)

  • The core circuitry consists of a voltage follower and a logic inverter

  • The BS register comprises 14 cells, ordered as follows: TBIC control structure (4 cells), ABM control structures (4+4 cells) and DBMs (1+1 cells)

An 8-bit instruction register is to be implemented, supporting (for the moment) the four mandatory instructions (EXTEST, S/P, PROBE, BYPASS), instruction codes being as follows:

  • EXTEST and BYPASS: as defined in the standard (respectively $00 and $FF)

  • PROBE: $01