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Chapter 5 Resets, Interrupts, and General System Control
MC9S08DZ128 Series Data Sheet, Rev. 1
Freescale Semiconductor
91
5.6
Low-Voltage Detect (LVD) System
The MC9S08DZ128 Series includes a system to protect against low-voltage conditions in order to protect
memory contents and control MCU system states during supply voltage variations. The system is
comprised of a power-on reset (POR) circuit and a LVD circuit with trip voltages for warning and
detection. The LVD circuit is enabled when LVDE in SPMSC1 is set to 1. The LVD is disabled upon
entering any of the stop modes unless LVDSE is set in SPMSC1. If LVDSE and LVDE are both set, then
the MCU cannot enter stop2 (it will enter stop3 instead), and the current consumption in stop3 with the
LVD enabled will be higher.
5.6.1
Power-On Reset Operation
When power is initially applied to the MCU, or when the supply voltage drops below the power-on reset
rearm voltage level, VPOR, the POR circuit will cause a reset condition. As the supply voltage rises, the
LVD circuit will hold the MCU in reset until the supply has risen above the low-voltage detection low
threshold, VLVDL. Both the POR bit and the LVD bit in SRS are set following a POR.
5.6.2
Low-Voltage Detection (LVD) Reset Operation
The LVD can be congured to generate a reset upon detection of a low-voltage condition by setting
LVDRE to 1. The low-voltage detection threshold is determined by the LVDV bit. After an LVD reset has
occurred, the LVD system will hold the MCU in reset until the supply voltage has risen above the
low-voltage detection threshold. The LVD bit in the SRS register is set following either an LVD reset or
POR.
6
0xFFF2/0xFFF3
Vtpm1ch1
TPM1
CH1F
CH1IE
TPM1 channel 1
5
0xFFF4/0xFFF5
Vtpm1ch0
TPM1
CH0F
CH0IE
TPM1 channel 0
4
0xFFF6/0xFFF7
Vlol
MCG
LOLS
LOLIE
MCG loss of lock
3
0xFFF8/0xFFF9
Vlvd
System
control
LVWF
LVWIE
Low-voltage warning
2
0xFFFA/0xFFFB
Virq
IRQ
IRQF
IRQIE
IRQ pin
1
0xFFFC/0xFFFD
Vswi
Core
SWI Instruction
—
Software interrupt
0
0xFFFE/0xFFFF
Vreset
System
control
COP,
LOC,
LVD,
RESET,
ILOP,
ILAD,
POR,
BDFR
COPT
CME
LVDRE
—
Watchdog timer
Loss-of-clock
Low-voltage detect
External pin
Illegal opcode
Illegal address
Power-on-reset
BDM-forced reset
1 Vector priority is shown from lowest (rst row) to highest (last row). For example, Vreset is the highest priority vector.
Table 5-1. Vector Summary1
Vector
Number
Address
(High/Low)
Vector
Name
Module
Source
Enable
Description