Oki’s ARM MCUs has built in Embedded-ICE on-chip debug hardware that enables non-intrusive debugging through the JTAG interface. The nTRST JTAG reset pin, allows resetting of the Embedded-ICE debug hardware independent of resetting the MCU core and peripherals. During JTAG debugging, it is critical for this pin to be controlled through the JTAG ICE adapter being used. However,, in the final user product that does not require JTAG debugging, this pin should be tied active low. This will place the MCU’s Embedded-ICE circuit, into active reset. For the MCU to operate successfully, the nTRST pin must toggle during power-on-reset. If this is not done, the MCU may go into an unknown state and not come out of Reset.