Inevitable use of TAP domains in SOCs

摘要

The 1149.1 TAP controller has proven to be an effective test interface for ICs on boards using its standard 4 pin interface (TCK, TMS, TDI, TDO). One of the most important features of the TAP is its Protocol, which provides an easy to follow Plug & Play IC test interface. This Protocol defines and enforces; (1) a Test Reset Mode, (2) a Run/Test Idle Mode, (3) an Instruction Scan Mode, and (4) a Data Scan Mode. IC level WEE standards that currently use the TAP Protocol include; IEEE 1149.1 (the Boundary Scan Standard), WEE 1149.4 (the Mixed Signal Test Bus Standard), IEEE P1149.6 (a proposed Advanced Digital Interconnect Test Standard), WEE 1532 (an In-System Programming Standard), and WEE 5001 (a Silicon Debug Standard). Further, numerous companies/consortiums use the TAP protocol at IC level to support various silicon debug, emulation, and code development strategies. As these users of TAPs migrate their products from individual ICs to reusable IP Cores, it appears inevitable that Systems-on-Chip (SOC) will include more and more embedded TAP domains.