PXS20RM Datasheet, PDF (1127/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Nexus Port Controller (NPC)
• RDY pin support to increase the transfer rate of the IEEE 1149.1 port for large data read requests
(supported on cut2/3 only)
34.2.3 Modes of operation
The NPC block uses the JCOMP input, the censorship status , and an internal power-on reset indication as
its primary reset signals. Upon exit of reset, the mode of operation is determined by the Port Configuration
Register (PCR) settings.
34.2.3.1 Reset
The NPC block is asynchronously placed in reset when either power-on reset is asserted, JCOMP is not
set for Nexus access, the device enters censored mode , or the TAP controller state machine is in the
Test-Logic-Reset state. Holding TMS high for 5 consecutive rising edges of TCK guarantees entry into the
Test-Logic-Reset state regardless of the current TAP controller state. Following negation of power-on
reset, the NPC remains in reset until the system clock achieves lock. The NPC is unaffected by other
sources of reset. While in reset, the following actions occur:
• The TAP controller is forced into the Test-Logic-Reset state
• The auxiliary output port pins are negated
• The TDI, TMS, and TCK TAP inputs are ignored (when in power-on reset, censored mode or
JCOMP not set for NPC operation only)
• Registers default back to their reset values
34.2.3.2 Disabled-Port Mode
In disabled-port mode, auxiliary output pin port enable signals are negated, thereby disabling message
transmission. Any debug feature that generates messages can not be used. The primary features available
are class 1 features and read/write access to the registers. Class 1 features include the ability to trigger a
breakpoint event indication through EVTO.
34.2.3.3 Full-Port Mode
Full-port mode (FPM) is entered by asserting the MCKO_EN and FPM bits in the PCR. All trace features
are enabled or can be enabled by writing the configuration registers via the TAP. The number of MDO pins
available is device-specific.
34.2.3.4 Reduced-Port Mode
Reduced-port mode (RPM) is entered by asserting the MCKO_EN bit and deasserting the FPM bit in the
PCR. All trace features are enabled or can be enabled by writing the configuration registers via the TAP.
The number of MDO pins available is device-specific.
34.2.3.5 Censored Mode
When the device is in censored mode, reading the contents of internal flash externally is not allowed. To
prevent Nexus modules from violating censorship, the NPC is held in reset when in censored mode,
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
34-3