6.2.4 Reset Pin
For all reset sources except a VLLS Wakeup that does not occur via the RESET pin, the
RESET pin is driven low by the MCU for at least 128 bus clock cycles and until flash
initialization has completed.
After flash initialization has completed, the RESET pin is released, and the internal Chip
Reset negates after the RESET pin is pulled high. Keeping the RESET pin asserted
externally delays the negation of the internal Chip Reset.
6.2.5 Debug resets
The following sections detail the debug resets available on the device.
6.2.5.1 JTAG reset
The JTAG module generate a system reset when certain IR codes are selected. This
functional reset is asserted when EzPort, EXTEST, HIGHZ and CLAMP instructions are
active. The reset source from the JTAG module is released when any other IR code is
selected. A JTAG reset causes the RCM's SRS1[JTAG] bit to set.
6.2.5.2
nTRST reset
The nTRST pin causes a reset of the JTAG logic when asserted. Asserting the nTRST pin
allows the debugger to gain control of the TAP controller state machine (after exiting
LLS or VLLSx) without resetting the state of the debug modules.
The nTRST pin does not cause a system reset.
6.2.5.3
Resetting the Debug subsystem
Use the CDBGRSTREQ bit within the SWJ-DP CTRL/STAT register to reset the debug
modules. However, as explained below, using the CDBGRSTREQ bit does not reset all
debug-related registers.
CDBGRSTREQ resets the debug-related registers within the following modules:
• SWJ-DP
• AHB-AP
Reset
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
176 NXP Semiconductors
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