Executing debug instructions

Apparatus for processing data, said apparatus comprising:

• a main processor driven by a main processor clock signal at a main processor clock frequency;
• debug logic at least a portion of which is driven by a debug clock signal at a debug clock frequency, said debug clock frequency being different from said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• and
• an instruction transfer register into which a data processing instruction is transferred by said debug logic and from which said data processing instruction is read by said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug logic triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal, wherein said main processor includes an instruction pipeline and, when switched from said normal mode to said debug mode, said debug logic controls said main processor to drain said instruction pipeline before any data processing instruction is read from said instruction transfer register by said main processor.

Apparatus for processing data, said apparatus comprising:

• a main processor driven by a main processor clock signal at a main processor clock frequency;
• debug logic at least a portion of which is driven by a debug clock signal at a debug clock frequency, said debug clock frequency being different from said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• and
• an instruction transfer register into which a data processing instruction is transferred by said debug logic and from which said data processing instruction is read by said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug logic triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal, wherein said debug logic triggers a switch from said normal mode to said debug mode in response to one or more of:
• execution of a breakpoint instruction;
• an external breakpoint signal;
• a breakpoint trigger;
• and a watchpoint trigger.

Apparatus for processing data, said apparatus comprising:

• a main processor driven by a main processor clock signal at a main processor clock frequency;
• debug logic at least a portion of which is driven by a debug clock signal at a debug clock frequency, said debug clock frequency being different from said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• and
• an instruction transfer register into which a data processing instruction is transferred by said debug logic and from which said data processing instruction is read by said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug logic triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal, wherein said data processing instruction is loaded into said instruction transfer register via a serial scan chain.

Apparatus for processing data, said apparatus comprising:

• a main processor driven by a main processor clock signal at a main processor clock frequency;
• debug logic at least a portion of which is driven by a debug clock signal at a debug clock frequency, said debug clock frequency being different from said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• and
• an instruction transfer register into which a data processing instruction is transferred by said debug logic and from which said data processing instruction is read by said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug logic triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal, comprising a data transfer register into which a data value is written and from which a data value is read by said debug logic, said main processor having access to said data transfer register whilst still driven by said main processor clock signal.

Apparatus for processing data, said apparatus comprising:

• a main processor driven by a main processor clock signal at a main processor clock frequency;
• debug logic at least a portion of which is driven by a debug clock signal at a debug clock frequency, said debug clock frequency being different from said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• and
• an instruction transfer register into which a data processing instruction is transferred by said debug logic and from which said data processing instruction is read by said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug logic triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal, wherein said debug logic includes a debug coprocessor coupled to said main processor via a coprocessor bus and driven by said main processor clock signal.

A method of processing data, said method comprising the steps of:

• driving a main processor with a main processor clock signal at a main processor clock frequency, said main processor in a non-debug mode performing normal data processing operations;
• driving debug logic with a debug clock signal at a debug clock frequency, said debug clock frequency being different to said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• transferring a main processor compatible data processing instruction into an instruction transfer register using said debug logic;
• and
• reading said data processing instruction from said instruction transfer register using said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug logic triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal.

Apparatus for processing data, said apparatus comprising:

• a main processor driven by a main processor clock signal at a main processor clock frequency, said main processor in a non-debug mode performs normal data processing operations;
• a debut, controller at least partially driven by a debug clock signal at a debug clock frequency, said debug clock frequency being different from said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• and
• an instruction transfer register into which a main processor compatible data processing instruction is transferred by said debug controller and from which said data processing instruction is read by said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug controller triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal.

A method of processing data, said method comprising the steps of:

• driving a main processor with a main processor clock signal at a main processor clock frequency, said main processor in a non-debug mode performing normal data processing operations;
• driving debug logic with a debug clock signal at a debug clock frequency, said debug clock frequency being different to said main processor clock frequency and said main processor clock signal being asynchronous with said debug clock signal;
• transferring a main processor compatible data processing instruction by a serial scan chain into an instruction transfer register using said debug logic;
• and
• reading said data processing instruction from said instruction transfer register using said main processor;
• wherein
• when switched from a normal mode to a debug mode said main processor continues to be driven by said main processor clock signal executing no-operation instructions until a data processing instruction is present within said instruction transfer register and said debug logic triggers said main processor to read and execute said data processing instruction whilst still driven by said main processor clock signal.