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Document # 001-20559 Rev. *D
POR and LVD
31.2
Register Definitions
The following registers are associated with the POR and LVD, and are listed in address order. The register descriptions below
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 should always be written with a value of ‘0’. For a complete table of the POR and LVD registers, refer to the
“Summary Table of the System Resource Registers” on page 272
31.2.1
VLT_CR Register
The Voltage Monitor Control Register (VLT_CR) is used to
set the trip points for POR, LVD, and the supply pump.
The VLT_CR register is cleared by all resets, which can
cause reset cycling during very slow supply ramps to 5V
when the POR range is set for the 5V range. This is
because the reset clears the POR range setting back to 3V
and a new boot/start up occurs (possibly many times). The
user can manage this with sleep mode and/or reading volt-
age status bits, if such cycling is an issue.
Bits 5 and 4: PORLEV[1:0].
These bits set the Vdd level at
which PPOR switches to one of three valid values. Note that
11b is a reserved value and therefore should not be used.
The three valid settings for these bits are:
❐
00b (3V or 2.4V operation
❐
01b (4.5V or 3.0V operation
❐
10b (4.75V operation)
See the “DC POR and LVD Specifications” table in the Elec-
trical Specifications section of the PSoC device data sheet
for voltage tolerances for each setting.
Bit 3: LVDTBEN.
This bit is AND’ed 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 3 MHz or EXTCLK /
8.
Bits 2 to 0: VM[2:0].
These bits set the Vdd level at which
LVD and the Pump Comparator switches.
For additional information, refer to the
.
31.2.2
VLT_CMP Register
The Voltage Monitor Comparators Register (VLT_CMP) is
used to read the state of internal supply voltage monitors.
Bit 3: NoWrite.
This bit is only used in PSoC devices with a
2.4V minimum POR. It reads the state of the Flash write
voltage monitor.
Bit 2: PUMP.
This bit reads the state of the Switch Mode
Pump Vdd comparator. The trip points for both LVD and
PUMP are set by VM[2:0] in the VLT_CR register.
Bit 1: LVD.
This bit reads the state of the low voltage
detect comparator. The trip points for both LVD and PUMP
are set by VM[2:0] in the VLT_CR register.
Bit 0: PPOR.
This bit reads back the state of the PPOR
output. This can only be meaningfully read with POR-
LEV[1:0] set to disable PPOR. In that case, the PPOR sta-
tus bit shows the comparator state directly.
For additional information, refer to the
.
Add.
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,E3h
PORLEV[1:0]
LVDTBEN
VM[2:0]
RW : 00
Add.
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,E4h
PUMP
LVD
PPOR
R : 00
Содержание PSoC CY8C23533
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