JTAG can only be used in slave boot mode. An external host computer acts as the master to load the boot components into the OCM, DDR memory, or FPGA using a JTAG connection.
Note
The PS CPU remains in idle mode while the boot image loads. The slave boot method is always a non-secure mode of booting.
In JTAG boot mode, the CPU enters halt mode immediately after it disables access to all security related items and enables the JTAG port. You must download the boot images into the DDR memory before restarting the CPU for execution.