WIR mode is latched from boot mode (see Section 33.3.2, Boot Modes) and allows the user to hold a secondary TAP module in reset state when a reset is applied (and thus, extend the reset). This mode lets the user control the following system level activities:
- Gain emulation control of any processor in a power domain at POR
- Capture and extend system-generated functional resets while running (under emulation control or not)
- Hold an entire power domain in reset until emulation control of the subsystem can be established
- Stall the entire system while reset is extended to a power domain
- Reset extension is visible external to the power domain.
- Debug execution of code from the first cycle of execution
- Prevent processor execution of random instructions in uninitialized program memory at power up
- Download code before any code execution takes place
- Coordinate debug initialization across multiple cores before code execution begins
WIR mode extends only the processor reset. During reset extension, the debugger can still access modules such as L2 memory and MMU, even if they are embedded in the device subsystem affected by WIR.
When the debugger task is complete, the DTC releases the subsystem reset by programming the corresponding ICEPick TAP control register.