Shared channel masks in on-product test compression system

[0020]Aspects of the present disclosure relate to testing electronic components, more particular aspects relate to shared channel masks in an on-product test compression (OPTC) system and a method of sorting and combining test patterns of hierarchal test blocks (HTB) of scan channels to cycle patterns concurrently while minimizing over-masking. A mask is required when a scan channel latch produces and indeterminate also referred to as an X-state result when a test pattern is cycled through it. Masks may be shared between scan channels and HTBs. The sharing may result in over-masking where a mask is enabled for one scan channel or HTB that needs the mask but inadvertently masks good results from other scan channels or HTBs. The method includes creating individual tests for each unique HTB and sorting the patterns of each test into mask sets. The mask sets are defined by the number of masks each pattern requires. The mask sets of each are then combined to run concurrently in a way tha...