ERAD monitors the CPU interfaces in a non-intrusive manner and also monitors some critical CPU internal buses and signals that convey information about the CPU code execution and pipeline. Most of the critical CPU interfaces are monitored by a comparator unit, which can be configured to match any address/data/instruction patterns that appear on the CPU interface and generate events based on this, as shown in Figure 1-2. There are multiple such units that can generate multiple events in parallel with different pattern matching capabilities. The comparator supports bit masking while comparing, which helps to detect/trigger events on ranges and not just discrete times alone. A simple example would be to generate an event when an address of interest is accessed for a read or write.

Other examples would be to trigger an event if code access goes beyond a certain safe zone or detecting a stack overflow as shown in the examples to follow.

The following is a list of CPU interfaces that can be monitored by EBC (F28004x):

• VPC - Program Counter
• DRAB - Data Read Address Bus
• DRDB - Data Read Data Bus
• DWAB- Data Write Address Bus
• DWDB- Data Write Data Bus
• PAB - Program/Instruction fetch bus