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enCoRe™ V CY7C643xx, enCoRe™ V LV CY7C604xx TRM, Document No. 001-32519 Rev *H
122
POR and LVD
17.2
Register Definitions
The following registers are associated with the POR and LVD, and are listed in address order. The following register descrip-
tions have an associated register table showing the bit structure. The bits that are grayed out in the register tables are
reserved bits and are not detailed in the register descriptions that follow. Reserved bits must always be written with a value of
‘0’. For a complete table of the POR registers, refer to the
Summary Table of the System Resource Registers on page 93
17.2.1
VLT_CR Register
The Voltage Monitor Control Register (VLT_CR) sets the trip
points for POR, MON1 and LVD.
The VLT_CR register is cleared by all resets. This can cause
reset cycling during very slow supply ramps to 5 V when the
MON1 range is set for the 5-V range. This is because the
reset clears the MON1 range setting back to 1.8 V and a
new boot or startup occurs (possibly many times). You can
manage this with sleep mode or reading voltage status bits if
such cycling is an issue.
Bit 7: HPOR.
This bit along with PORLEV sets one of the
four values for the PPOR trip voltage. See
Bits 5 and 4: PORLEV[1:0].
These bits along with HPOR
sets one of the four values for the PPOR trip voltage. See
.
See the “DC POR and LVD Specifications” table in the Elec-
trical Specifications section of the enCoRe V device data-
sheet for voltage tolerances for each setting.
Bit 3: LVDTBEN.
This bit is ANDed with LVD to produce a
throttle back signal that reduces CPU clock speed when low
voltage conditions are detected. When the throttle back sig-
nal is asserted, the CPU speed bits in the OSC_CR0 regis-
ter are reset, forcing the CPU speed to its reset state.
Bits 2 to 0: VM[2:0].
These bits set the Vdd level at which
the LVD Comparator switches.
See the “DC POR and LVD Specifications” table in the Elec-
trical Specifications section of the enCoRe V device data-
sheet for voltage tolerances for each setting.
For additional information, refer to the
17.2.2
VLT_CMP Register
The Voltage Monitor Comparators Register (VLT_CMP)
reads the state of internal supply voltage monitors.
Bit 1: LVD.
This bit reads the state of the LVD comparator.
Zero Vdd is above the trip point. The trip points for LVD are
set by VM[2:0] in the VLT_CR register.
For additional information, refer to the
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,E3h
HPOR
PORLEV[1:0]
LVDTBEN
VM[2:0]
RW : 00
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,E4h
LVD
RW : 0