Resets, Interrupts, and General System Control
MCF51CN128 Reference Manual, Rev. 6
5-20
Freescale Semiconductor
7
6
5
4
3
2
1
0
R
LVWF
0
LVDV
LVWV
LVWIE
0
0
0
W
LVWACK
POR:
0
0
0
0
0
0
0
0
LVR:
0
0
U
U
0
0
0
0
Any other
reset:
0
0
U
U
0
0
0
0
1
LVWF is set when V
Supply
transitions below the trip point or after reset and V
Supply
is already below V
LVW
.
2
U = Unaffected by MCU Reset.
Figure 5-10. System Power Management Status and Control 3 Register (SPMSC3)
Table 5-14. SPMSC3 Register Field Descriptions
Field
Description
7
LVWF
Low-Voltage Warning Flag —
The LVWF bit indicates the low voltage detect event status.
0 Low voltage warning not present.
1 Low voltage warning is present or was present.
6
LVWACK
Low-Voltage Warning Acknowledge —
Writing a 1 to LVWACK clears LVWF if a low voltage warning is no
longer present.
5
LVDV
Low-Voltage Detect Voltage Select —
The LVDV bit selects the LVD trip point voltage (V
LVD
).
0 Low trip point selected (V
LVD
= V
LVDL
).
1 High trip point selected (V
LVD
= V
LVDH
).
4
LVWV
Low-Voltage Warning Voltage Select
— The LVWV bit selects the LVW trip point voltage (V
LVW
).
0 Low trip point selected (V
LVW
= V
LVWL
).
1 High trip point selected (V
LVW
= V
LVWH
).
3
LVWIE
Low-Voltage Warning Interrupt Enable
— This bit enables hardware interrupt requests for LVWF.
0 Hardware interrupt disabled (use polling).
1 Request a hardware interrupt when LVWF is set.
2–0
Reserved, must be cleared.
Table 5-15. LVD and LVW Trip Point Typical Values
1
1
See the
MCF51CN128 Data Sheet
for minimum and maximum values.
LVDV:LVWV
LVW Trip Point
LVD Trip Point
00
V
LVWL
= 2.16
V
LVDL
= 1.84
01
V
LVWL
= 2.21
V
LVDL
= 1.92
10
Not Recommended
V
LVWL
= 2.46
V
LVDL
= 2.33
11
V
LVDL
= 2.41