A system and method for handling exception causing events

A first processing unit comprising:

• execution circuitry to execute program code;
• and
• a control interface mapped to memory address space of a second processing unit and configured to provide the second processing unit with direct mapped access to state information of the first processing unit;
• the first processing unit being responsive to at least one exception causing event to enter a halted mode where the execution circuitry stops execution of the program code, and a trigger event is issued;
• the control interface being arranged to be accessible to the second processing unit whilst the second processing unit is executing an exception handling routine in response to the trigger event, to enable the second processing unit to access and modify the state information of the first processing unit as required by the exception handling routine;
• the first processing unit being arranged, when the second processing unit has completed the exception handling routine, to exit the halted mode and resume execution of the program code.

A second processing unit comprising:

• execution circuitry to execute an exception handling routine in response to a trigger event issued by a first processing unit, the trigger event indicating that the first processing unit has entered a halted mode where execution of program code by the first processing unit has been halted;
• and
• a communication interface via which the second processing circuitry is arranged to access a control interface of the first processing unit whilst executing the exception handling routine, the control interface being mapped to memory address space of the second processing unit and configured to provide the second processing unit with direct mapped access to state information of the first processing unit;
• the second processing unit being arranged to access the state information of the first processing unit via the control interface in order to modify the state information as required by the exception handling routine;
• and
• the second processing unit being arranged on completion of the exception handling routine to cause the first processing unit to exit the halted mode and resume execution of the program code.

A method of handling exception causing events in a system having a first processing unit to execute program code, and a second processing unit, comprising:

• providing the first processing unit with a control interface mapped to memory address space of the second processing unit and configured to provide the second processing unit with direct mapped access to state information of the first processing unit;
• responsive to at least one exception causing event within the first processing unit, causing the first processing unit to enter a halted mode where the first processing unit stops execution of the program code, and issues a trigger event;
• causing the second processing unit to be responsive to the trigger event to execute an exception handling routine during which the second processing unit accesses the state information of the first processing unit via the control interface in order to modify the state information as required by the exception handling routine;
• and
• on completion of the exception handling routine by the second processing unit, causing the first processing unit to exit the halted mode and resume execution of the program code.