Multiplex-operated control connections for programming within the system and for Boundary Scan testing using automated systems with a programmable logic circuit of high integration density

摘要

A structure and a method to implement in-system programming (ISP) and boundary-scan testing in an integrated circuit using the same pins to control both functions. The SDI, SCLK, MODE and SDO connections required for in-system programming and the TDI, TCK, TMS and TDO connections required for boundary-scan testing are multiplexed such that they are provided from the same four pins. An in-system programming enable pin is used to control the multiplexing of these pins. In an alternative embodiment, both in-system programming and boundary-scan testing are performed using the same pins and the same state machine. The test logic architecture specified in IEEE Standard 1149.1-1990 is utilized. To implement the in-system programming instructions, the instruction register of Std. 1149.1-1990 is modified to include private instructions which perform the desired programming functions. IMAGE