SWCU193A April 2023 – August 2024 CC2340R2 , CC2340R5 , CC2340R5-Q1
The SWD debug port is activated whenever a long sequence of bits is clocked into the SWDIO pin by edges on the SWDCK pin. The sequence is detected in all device power states except for reset but including shutdown by a module called IceMelter and the SWD connection status remains until:
In boot, if SWD is connected, the device management interface SACI is always entered even if there is a valid bootloader or application to run. SACI has a configurable timeout for when to continue boot if there is no SWD activity, otherwise SACI waits until instructed by a SACI command over SWD before continuing boot. Communication with SACI is done through SWD using the SEC-AP mailbox.
To allow debugging across resets or shutdown scenarios, SACI commands exist for continuing boot and halting CPU right before application (or bootloader if permitted) is entered. At this point hardware debug breakpoints must be resubmitted as these do not survive the reset. Debug (re)authentication SACI commands can also be required if dictated by CCFG.debugCfg.
See Chapter 5 or Section 8.3 for more details.