SLAU319AF July 2010 – September 2022
Devices with dedicated JTAG pins use the TCK pin instead of the TEST pin.
The BSL program execution starts whenever the TCK pin has received a minimum of two falling edges and TCK is low while RST/NMI rises from low to high (BSL entry method, see Figure 1-3). This level transition triggering improves BSL start-up reliability.
The recommended minimum time for pin states is 250 ns. See the device-specific errata for any differences, because some 5xx and 6xx device revisions have specific entry sequence requirements.