Apparatus and method for performing a multi-value polling operation in a JTAG data stream

A method of providing a polling operation in which a plurality of expected data types are compared to a logic value group in a received data stream in a JTAG protocol scan controller of a test and debug system;

• the method comprising;
• associating each field of a plurality of register fields of a scan controller expected value register with a data type, wherein a value indicative of inclusion in a polling operation is stored in each field associated with an expected data type;
• decoding a group of logic values from a received target processor data stream to provide a resulting signal, wherein each resulting signal corresponds to a field of the expected value register;
• and
• comparing the resulting signal with a signal provided from a field of the scan controller expected value register.

A test and debug system using a JTAG protocol for testing a target processor, the system comprising:

• a test and debug unit;
• and
• a scan controller responsive to the test and debug system for implementing a polling operation, the scan controller including:
• a poll unit, the poll unit having:
• an expected value register comprising a plurality of data type fields, each field associated with a data type, wherein each field associated with an expected data type has a value stored therein indicating that the data type is included in a polling operation;
• a decoder unit receiving selected logic values from the received data stream of a target processing unit, the decoder unit providing a resulting signal corresponding to the selected logic values:
• wherein the resulting signal corresponds to a data type field of the expected value register;
• and
• a comparison unit comparing the resulting signal with a logic signal from a data type field of the expected value register, a positive comparison providing a successful polling operation.