P912XDP512F0MFVR datasheet(565/1350 Pages) FREESCALE

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Chapter 14 Voltage Regulator (S12VREG3V3V5)

MC9S12XDP512 Data Sheet, Rev. 2.17

Freescale Semiconductor

565

14.4.2.2

Reduced Power Mode

In reduced power mode, the gate of the output transistor is connected directly to a reference voltage to

reduce power consumption.

14.4.3

Low-Voltage Detect (LVD)

Subblock LVD is responsible for generating the low-voltage interrupt (LVI). LVD monitors the input

voltage (VDDA–VSSA) and continuously updates the status ﬂag LVDS. Interrupt ﬂag LVIF is set whenever

status ﬂag LVDS changes its value. The LVD is available in FPM and is inactive in reduced power mode

or shutdown mode.

14.4.4

Power-On Reset (POR)

This functional block monitors VDD. If VDD is below VPORD, POR is asserted; if VDD exceeds VPORD,

the POR is deasserted. POR asserted forces the MCU into Reset. POR Deasserted will trigger the power-on

sequence.

14.4.5

Low-Voltage Reset (LVR)

Block LVR monitors the primary output voltage VDD. If it drops below the assertion level (VLVRA) signal,

LVR asserts; if VDD rises above the deassertion level (VLVRD) signal, LVR deasserts. The LVR function

is available only in full peformance mode.

14.4.6

Regulator Control (CTRL)

This part contains the register block of VREG_3V3 and further digital functionality needed to control the

operating modes. CTRL also represents the interface to the digital core logic.

14.4.7

Autonomous Periodical Interrupt (API)

Subblock API can generate periodical interrupts independent of the clock source of the MCU. To enable

the timer, the bit APIFE needs to be set.

The API timer is either clocked by a trimmable internal RC oscillator or the bus clock. Timer operation

will freeze when MCU clock source is selected and bus clock is turned off. See CRG speciﬁcation for

details. The clock source can be selected with bit APICLK. APICLK can only be written when APIFE is

not set.

The APIR[11:0] bits determine the interrupt period. APIR[11:0] can only be written when APIFE is

cleared. As soon as APIFE is set, the timer starts running for the period selected by APIR[11:0] bits. When

the conﬁgured time has elapsed, the ﬂag APIF is set. An interrupt, indicated by ﬂag APIF = 1, is triggered

if interrupt enable bit APIE = 1. The timer is started automatically again after it has set APIF.

The procedure to change APICLK or APIR[11:0] is ﬁrst to clear APIFE, then write to APICLK or

APIR[11:0], and afterwards set APIFE.

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