Device Reset Configuration
MPC5746R Hardware Design Guide, Rev. 1
NXP Semiconductors 23
5.1 External reset signals
MPC5746R devices feature two external reset signals:
• Power-on reset (PORST)
• External reset (RESET
)
Both external reset signals are bidirectional and active-low. RESET
indicates whether the device is active
(high signal) or in reset. It is in a weak pull-up state after the reset sequence has completed. An external
4.7 kΩ pull-up resistor on RESET is required. A falling edge on this pin will trigger a functional reset to
the Reset Generation Module (RGM). Holding this pin low will keep the device in the last phase of the
reset sequence (Phase3[Functional]).
After reset, PORST is configured as a weak pull-down for safety reasons. In case PORST is disconnected
the device will remain in reset. PORST is released when the device leaves the power-up state of the RGM.
PORST must be forced high externally so the device will leave the reset state. The internal weak pull-down
maximum current of PORST is 100 uA. It is recommended that an external 4.7 kΩ pull-up resistor be used
to ensure the PORST voltage level remains safely above the threshold.
Figure 12 illustrates the typical system configuration of RESET and PORST pins with the external
components.
Figure 12. example Circuitry for RESET & PORST pins
5.2 Reset Out (RSTOUT)
MPC5746R has an optional Reset out signal which can be used to notify external systems that the MCU
has been reset. Pin PJ[5] can be configured to drive the reset out signal (RSTOUT) without generating the
internal reset. RSTOUT will follow the RESET pin until reconfigured in software.
In a POR event RSTOUT is internally pull-up then actively drives low during reset PHASE3 and drives
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