%META:TOPICINFO{author="blundar" date="1077237440" format="1.0" version="1.1"}% MCU used in OBD0 MPFI ECUs that has zero internal code memory. requires the use of an external EPROM It is mostly 8051 compatible, and features a third timer like many other replacements. The main difference from a pure 8051 revolves around how the A5 instruction is handled.