SPRUJF2A March 2026 – March 2026 AM13E23019
By default on POR, debug connections are routed to a JTAG compliant interface known as JTAG-DP. The JTAG-DP interface requires four connections:
The JTAG interface uses the standard logic levels of the device for JTAG communication. See the device-specific data sheet for input and output logic levels for a given supply voltage (VDD). A TCK frequency of up to 40MHz is supported by the DEBUGSS.
During JTAG operation, the TMS/TDI/TCK line can be driven high or low by the debug probe while the TDO line can be driven high or low by the target device. The primary purpose of the pullup resistors on the TMS/TDI/TDO pins and the pulldown on TCK is to put the signals into a known state when no debug probe is attached. A minimum resistance of 100kΩ is recommended by Arm. The internal pullup/pulldown resistors fulfill this requirement and external resistors are not required for correct operation of the JTAG interface.
After a power-on reset (POR), AM13E230x devices configure the JTAG pins in JTAG mode with an internal pullup resistor enabled on the TMS/TDI/TDO lines and internal pullup enabled on the TCK line. If the device configuration has not permanently disabled all JTAG access, then the JTAG interface is enabled during the boot process and a debug probe can be connected to the DEBUGSS.