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Chapter 2 Port Integration Module (S12ZVMPIMV1)
MC9S12ZVM Family Reference Manual Rev. 1.3
Freescale Semiconductor
115
2.4.6
Over-Current Interrupt
In case of an over-current condition on PP0 (see Section
2.5.2, “Over-Current Protection on EVDD1
”) the
over-current interrupt flag PIFP[OCIF1] asserts. This flag generates an interrupt if the enable bit
PIEP[OCIE1] is set.
An asserted flag immediately forces the output pin low to protect the device. The flag must be cleared to
re-enable the driver.
2.5
Initialization and Application Information
2.5.1
Port Data and Data Direction Register writes
It is not recommended to write PORTx/PTx and DDRx in a word access. When changing the register pins
from inputs to outputs, the data may have extra transitions during the write access. Initialize the port data
register before enabling the outputs.
2.5.2
Over-Current Protection on EVDD1
Pin PP0 can be used as general-purpose I/O or due to its increased current capability in output mode as a
switchable external power supply pin (EVDD1) for external devices like Hall sensors.
EVDD1 is supplied by the digital pad supply VDDX.
An over-current monitor is implemented to protect the controller from short circuits or excess currents on
the output which can only arise if the pin is configured for full drive. Although the full drive current is
available on the high and low side, the protection is only available on the high side with a current direction
from EVDD1 to VSSX. There is also no protection to voltages higher than V
DDX
.
To power up the over-current monitor set the related OCPE1 bit in register PIMMISC.
In stop mode the over-current monitor is disabled for power saving. The increased current capability
cannot be maintained to supply the external device. Therefore when using the pin as power supply the
external load must be powered down prior to entering stop mode by driving the output low.
An over-current condition is detected if the output current level exceeds the threshold I
OCD
in run mode.
The output driver is immediately forced low and the over-current interrupt flag OCIFx asserts. Refer to
Section