NXP Semiconductors MPC5746R - Reset Pad (PORST, RESET) Electrical Characteristics

MPC5746R Hardware Design Guide, Rev. 1
Power Supply
NXP Semiconductors18
Figure 7. Logical connection between power domains
The actual threshold used for each LVD depends on the configuration of the device. This is configurable
by hardware (flash option bit settings) or by software (LVD event configuration through a register
interface). Once the power-on signal has been asserted, the device configuration is reset to default
power-up configuration; during the initialization phase, the device defaults to a pre-determined state for
each of the LVDs, HVDs, and the internal regulators. As the flash memory becomes available, the
differential read process allows the trimmed data to be available for trimming the internal LVDs, HVDs,
and regulators.
3.7.1 Power-up sequence
In this section, the assumption is made that all supplies are low when entering the power-up sequence.
Brown-out and power down sequences are discussed in following sections.
At the beginning of power-up, the internal power-on signal remains low due to the parasitic diodes. As
soon as the minimum threshold is reached on VDD_LV, the power-on signal is forced low. It remains low
until the power-up LVDs reach their upper (not trimmed) threshold. During power-up, all functional pins
are maintained in a known state as described in Table 12.
The power-up sequence is as follows:
1. Digital reset is asserted, ensuring that all module registers are reset to their power-on value.
2. The POWERUP state is exited when both VDD_LV and VDD_HV are above threshold.
Table 12. Functional Terminal State - Power-Up and Reset
Pin Type
POWERUP
Pad State
During RESET
Pad State
Out of RESET
Pad State
PORST strong pull-down weak pull-down weak pull-down
RESET strong pull-down weak pull-up weak pull-up
GPIO high impedance weak pull-up weak pull-up
ANALOG high impedance high impedance high impedance
ERROR high impedance high impedance high impedance
JCOMP high impedance weak pull-down weak pull-down
TCK high impedance weak pull-down weak pull-down
TMS high impedance weak pull-up weak pull-up
TDI high impedance weak pull-up weak pull-up
TDO high impedance high impedance high impedance
VDD_LV
VDD_HV_PMC
VDD_HV_IO_MAIN
VDD_HV_FLA
POWERUP