C8051F410/1/2/3
130
Rev. 1.1
SFR Definition 15.1. VDM0CN: VDD Monitor Control
Bit7:
VDMEN: VDD Monitor Enable.
This bit turns the VDD monitor circuit on/off. The VDD Monitor cannot generate system resets
Monitor can be allowed to stabilize before it is selected as a reset source.
Selecting the
VDD monitor as a reset source before it has stabilized may generate a system reset.
See Table 15.1 for the minimum VDD Monitor turn-on time. 0: VDD Monitor Disabled.
1: VDD Monitor Enabled (default).
Bit6:
VDDSTAT: VDD Status.
This bit indicates the current power supply status (VDD Monitor output).
0: VDD is at or below the VDD Monitor Threshold.
1: VDD is above the VDD Monitor Threshold.
Bit5:
VDMLVL: VDD Level Select.
0: VDD Monitor Threshold is set to VRST-LOW (default).
1: VDD Monitor Threshold is set to VRST-HIGH. This setting is recommended for any system
that includes code that writes to and/or erases Flash.
Bits4–0: Reserved. Read = Variable. Write = don’t care.
R/W
R
R/W
R
Reset Value
VDMEN
VDDSTAT VDMLVL Reserved Reserved Reserved Reserved Reserved 1v000000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
SFR Address:
0xFF
15.3. External Reset
The external RST pin provides a means for external circuitry to force the device into a reset state. Assert-
ing an active-low signal on the RST pin generates a reset; an external pullup and/or decoupling of the RST
pin may be necessary to avoid erroneous noise-induced resets. See
Table 15.1 for complete RST pin
specifications. The PINRSF flag (RSTSRC.0) is set on exit from an external reset.
15.4. Missing Clock Detector Reset
The Missing Clock Detector (MCD) is a one-shot circuit that is triggered by the system clock. If the system
clock remains high or low for more than 100 s, the one-shot will time out and generate a reset. After a
MCD reset, the MCDRSF flag (RSTSRC.2) will read ‘1’, signifying the MCD as the reset source; otherwise,
this bit reads ‘0’. Writing a ‘1’ to the MCDRSF bit enables the Missing Clock Detector; writing a ‘0’ disables
it. The state of the RST pin is unaffected by this reset.
15.5. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a ‘1’ to the C0RSEF flag (RSTSRC.5).
Comparator0 should be enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on
chatter on the output from generating an unwanted reset. The Comparator0 reset is active-low: if the non-