Apparatus and method for transferring multiple scan length signal groups for JTAG boundary scans
AssigneeTexas Instruments Incorporated
InventorsLee Larson, Henry Hoar
Life of this patent
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Abstract
In a JTAG test and debug environment, the signal groups for boundary scans can have several lengths including signal groups that are longer that the shift register out. A storage unit is provided with a plurality of storage location lengths. The boundary scan signal groups are stored in a location having a suitable storage capacity. The command that transfers the boundary scan signal group includes a parameter identifying the relevant location. The scan control unit, upon receiving the command, transfers the entire boundary scan signal group as a result this command even if several transfers through the shift register out are required.
Claims10
A test and debug system for testing a target processor, the system comprising:
- data transfer apparatus in the target processor to receiving data and for transferring data;
- a test access port in the target processor responsive to control signals, the control signals determining the state of the test and debug apparatus in the target processor;
- and
- a scan control unit, the scan control unit including:
- a processor responsive to commands for generating the control signals;
- at least one register responsive to signals from the processor for exchanging data with the data transfer apparatus;
- and
- a plurality of scan length storage units, the scan length storage units capable of storing signal groups of varying lengths.
In a JTAG test and debug system, a method for transferring a signal group greater than the shift register out under control of a scan control unit, the method comprising:
- storing the signal group in one of a group of storage locations having a variable signal storage capacity;
- and
- in response to command, the scan control unit transferring the signal group to a target processor in a plurality of transfers through the shift register out.
In a test and debug unit, a scan control unit comprising:
- a local processor responsive to at least one command;
- a shift register out, the shift register out shifting signals out of the scan control unit, and
- a storage unit having a plurality of storage locations, the storage locations having a variable number of storage locations;
- wherein the local processor, in response to a parameter in a command, shifts the signal group in a storage location designated by the parameter through the shift register out.
Dependencies are inferred from the claim text.