Tap, data input, output circuitry coupled to mode select lead

摘要

The present disclosure describes using the JTAG Tap's TMS and/or TCK terminals as general purpose serial Input/Output (I/O) Manchester coded communication terminals. The Tap's TMS and/or TCK terminal can be used as a serial I/O communication channel between; (1) an IC and an external controller, (2) between a first and second IC, or (3) between a first and second core circuit within an IC. The use of the TMS and/or TCK terminal as serial I/O channels, as described, does not effect the standardized operation of the JTAG Tap, since the TMS and/or TCK I/O operations occur while the Tap is placed in a non-active steady state.

主权项

1. Communication circuitry comprising:
A. interface leads including a data input lead, a mode select lead, a clock lead, and a data output lead; B. access port circuitry coupled to the interface leads and including controller circuitry connected to the mode select lead and the clock lead and having control outputs, an instruction register connected to the data input lead and the control outputs, and a data register connected to the data input lead and the control outputs; and C. serial communication circuitry separate from the access port circuitry, the serial communication circuitry including data input circuitry and data output circuitry coupled to the mode select lead and to the control outputs to input data and to output data on the mode select lead.