Freescale Semiconductor MK22FN256VDC12, Reference Manual

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Signal
multiplexing
Module signals
EzPort
Transfers
Crossbar
switch
Figure 3-25. EzPort configuration
Table 3-36. Reference links to related information
Topic Related module Reference
Full description EzPort EzPort
System memory map System memory map
Clocking Clock Distribution
Transfers Crossbar switch Crossbar switch
Signal Multiplexing Port control Signal Multiplexing
3.5.6.1 JTAG instruction
The system JTAG controller implements an EZPORT instruction. When executing this
instruction, the JTAG controller resets the core logic and asserts the EzPort chip select
signal to force the processor into EzPort mode.
3.5.6.2 Flash Option Register (FOPT)
The FOPT[EZPORT_DIS] bit can be used to prevent entry into EzPort mode during
reset. If the FOPT[EZPORT_DIS] bit is cleared, then the state of the chip select signal
(EZP_CS) is ignored and the MCU always boots in normal mode.
This option is useful for systems that use the EZP_CS/NMI signal configured for its NMI
function. Disabling EzPort mode prevents possible unwanted entry into EzPort mode if
the external circuit that drives the NMI signal asserts it during reset.
The FOPT register is loaded from the flash option byte. If the flash option byte is
modified the new value takes effect for any subsequent resets, until the value is changed
again.
3.6 Security
Chapter 3 Chip Configuration
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
Freescale Semiconductor, Inc. 91