Patent ID: 7412633

Claim:
An integrated circuit for processing data, said integrated circuit comprising: a functional circuit configured to perform data processing operations: a diagnostic circuit configured to perform diagnostic operations upon said functional circuit, and an interface circuit configured to use a bi-directional serial link to provide communications between said diagnostic circuit and an external diagnostic device, wherein said interface circuit and said external diagnostic device are configured when changing communication direction such that a sequence is followed comprising: (i) driving a signal carried on said bi-directional serial link to a park state having a predetermined signal value for a park state period with whichever one of said interface circuit and said external diagnostic device was serving as a data sender; (ii) providing for said signal carried on said bi-directional serial link to be substantially undriven and float at substantially said predetermined signal value for an undriven state period; (iii) driving said signal carried on said bi-directional serial link to a resume state having signal value opposite to said predetermined signal value for a resume state period with whichever one of said interface circuit and said external diagnostic device is to now serve as said data sender.