测试数据压缩是片上系统(System-on-chip,SoC)测试中的关键问题之一,用于有效地减少测试数据总量。本文提出了一种新颖的变长-变长压缩编码,称为AFDR(Advanced frequency-directed run-length)编码。它同时对0游程和1游程进行编码,并对等长游程赋以相同的编码,优化了仅仅考虑0游程的FDR(Frequency-directed run-length)码。此外,对游程长度为2的数据(即00和11)进行特殊处理,进一步地提高了压缩比。ISCAS89标准电路下的实验结果表明,AFDR编码的压缩效果明显优于FDR编码以及同类型的其他编码。 Test Data Compression is one of the key issues in system-on-chip (SoC) testing to effectively reduce the amount of test data. This paper presents a novel variable-length variable-length coding, called AFDR (Advanced frequency-directed run-length) coding. It encodes both 0 run and 1 run at the same time, assigns the same code to the run length, and optimizes the FDR (Frequency-directed run-length) code that only considers 0 run. In addition, special processing of run length 2 data (ie, 00 and 11) further increases the compression ratio. Experimental results under the ISCAS89 standard circuit show that AFDR compression is significantly better than FDR and other codes of the same type.