Datasheet

REV. 0
ADuC816
–47–
Power Supply Monitor
As its name suggests, the Power Supply Monitor, once enabled,
monitors both supplies (AVDD or DVDD) on the ADuC816. It
will indicate when any of the supply pins drop below one of
four user-selectable voltage trip points from 2.63 V to 4.63 V.
For correct operation of the Power Supply Monitor function,
AV
DD
must be equal to or greater than 2.7 V. Monitor function
is controlled via the PSMCON SFR. If enabled via the IEIP2
SFR, the monitor will interrupt the core using the PSMI bit in the
PSMCON SFR. This bit will not be cleared until the failing
power supply has returned above the trip point for at least
250 ms. This monitor function allows the user to save working
registers to avoid possible data loss due to the low supply condi-
tion, and also ensures that normal code execution will not
resume until a safe supply level has been well established. The
supply monitor is also protected against spurious glitches trig-
gering the interrupt circuit.
PSMCON Power Supply Monitor Control Register
SFR Address DFH
Power-On Default Value DEH
Bit Addressable No
DPMCAPMCIMSP1DPT0DPT1APT0APTNEMSP
Table XVIII. PSMCON SFR Bit Designations
Bit Name Description
7 CMPD DVDD Comparator Bit.
This is a read-only bit and directly reflects the state of the DVDD comparator.
Read “1” indicates the DVDD supply is above its selected trip point.
Read “0” indicates the DVDD supply is below its selected trip point.
6 CMPA AVDD Comparator Bit.
This is a read-only bit and directly reflects the state of the AVDD comparator.
Read “1” indicates the AVDD supply is above its selected trip point.
Read “0” indicates the AVDD supply is below its selected trip point.
5 PSMI Power Supply Monitor Interrupt Bit.
This bit will be set high by the MicroConverter if either CMPA or CMPD are low, indicating
low analog or digital supply. The PSMI bit can be used to interrupt the processor. Once CMPD
and/or CMPA return (and remain) high, a 250 ms counter is started. When this counter times
out, the PSMI interrupt is cleared. PSMI can also be written by the user. However, if either com-
parator output is low, it is not possible for the user to clear PSMI.
4 TPD1 DVDD Trip Point Selection Bits.
3 TPD0 These bits select the DVDD trip-point voltage as follows:
TPD1 TPD0 Selected DVDD Trip Point (V)
0 0 4.63
0 1 3.08
1 0 2.93
1 1 2.63
2 TPA1 AVDD Trip Point Selection Bits.
1 TPA0 These bits select the AVDD trip-point voltage as follows:
TPA1 TPA0 Selected AVDD Trip Point (V)
0 0 4.63
0 1 3.08
1 0 2.93
1 1 2.63
0 PSMEN Power Supply Monitor Enable Bit.
Set to “1” by the user to enable the Power Supply Monitor Circuit.
Cleared to “0” by the user to disable the Power Supply Monitor Circuit.
REV. A