The paper presents a novel test data compression scheme. This low-silicon-area solution builds on the isometric compression paradigm, but makes it more flexible, elevates encoding efficiency to values unachievable through any conventional type of sequential compression, and ensures high test coverage due to programmable selection of full toggle scan chains. The presented approach follows from a fundamental observation that only a few specified positions in test cubes are necessary to detect faults, while the remaining ones have alternative sites. Such test cubes are used to form circular test templates which synergistically control a decompressor and guide ATPG to find assignments yielding highly compressible test cubes. A redesigned decompressor is also capable of reducing switching rates in scan chains with a new test power control scheme. Experimental results obtained for large industrial designs confirm superiority of the proposed scheme over state-of-the-art techniques and are reported herein.