Freescale Semiconductor, Inc.
Low-Voltage Inhibit (LVI) Module
Functional Description
Once an LVI reset occurs, the MCU remains in reset until VDD rises
above a voltage, LVITRIPR. VDD must be above LVITRIPR for only one
CPU cycle to bring the MCU out of reset. See 15.4.2 Forced Reset
Operation. The output of the comparator controls the state of the
LVIOUT flag in the LVI status register (LVISR).
An LVI reset also drives the RST pin low to provide low-voltage
protection to external peripheral devices.
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read: LVIOUT
0
0
0
0
0
0
0
LVI Status Register
$FE0F
(LVISR) Write:
See page 212.
Reset:
0
0
0
0
0
0
0
0
= Unimplemented
Figure 15-2. LVI I/O Register Summary
15.4.1 Polled LVI Operation
In applications that can operate at VDD levels below the LVITRIPF level,
software can monitor VDD by polling the LVIOUT bit. In the configuration
register, the LVIPWR bit must be at logic 1 to enable the LVI module, and
the LVIRST bit must be at logic 0 to disable LVI resets.
15.4.2 Forced Reset Operation
In applications that require VDD to remain above the LVITRIPF level,
enabling LVI resets allows the LVI module to reset the MCU when VDD
falls to the LVITRIPF level and remains at or below that level for nine or
more consecutive CPU cycles. In the configuration register, the LVIPWR
and LVIRST bits must be at logic 1 to enable the LVI module and to
enable LVI resets.
MC68HC908AS60 — Rev. 1.0
Technical Data
Low-Voltage Inhibit (LVI) Module
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