EFLOW EF-Series - Low Power Modes

EF-Series Instruction Manual
Rev 2/01 2-13
The software watchdog is controlled by the Main Electronics Board. This watchdog checks the
software for validity every 1.2 seconds. If necessary, the software is automatically reset. The
hardware watchdog is controlled by the Main Electronics Board and monitors the power to the
hardware. If this voltage drops below 4.75 volts, the unit is automatically shut down.
RTD automatic temperature compensation is tested at approximately every 5 degrees Celsius temper-
ature change of the board temperature.
The EF-Series unit monitors its orifice-metering Sensor for accurate and continuous operation.
Voltage for charging the supercapacitor is checked to ensure that it is continuously applied when the
EF-Series unit is powered.
A memory validity self-test is performed to ensure the integrity of memory.
2.4.10 Low Power Modes
The processor used in the EF-Series unit is capable of low power operation under predetermined
conditions. These features are available because of the Phase Lock Loop (PLL) used to control the
speed of the system clock. The base crystal frequency is 3.6863 MHz and is raised by the PLL to 14.7
MHz for normal system operation. During the low power modes, the PLL and oscillator are in various
states of shutdown. Two low power modes are supported: Standby and Sleep (also called Doze).
♦ Standby — This mode is used during periods of inactivity. When the operating system cannot
find a task to run, the EF-Series unit enters Standby mode. Processor loading is calculated by
using the amount of time spent in Standby mode. This mode keeps the clocks running and
communications active with baud clocks running. A Periodic Interrupt Timer (PITR) wakes up
the EF-Series unit and starts the normal operating mode.
Wake-up from Standby occurs when the EF-Series unit receives a:
♦ Timed / Alarmed interrupt from the Real-Time Clock.
♦ Signal from the Operator Interface port – LOI.
♦ Signal from Connector P10 (built-in I/O) or I/O card
♦ Signal Carrier Detect (CD) from a communications board – COM1.
♦ Signal Ring Indicator (RI) from a communications board – COM1.
♦ Sleep — This mode is used if a low battery voltage is detected. The battery voltage measured
by diagnostic input point E1 is compared to the low-low alarm limit associated with this point.
This limit value defaults to 10.6 volts.
Wake-up from Sleep occurs when the EF-Series unit receives a:
♦ Timed / Alarmed interrupt from the Real-Time Clock.
♦ Signal from the Operator Interface port – LOI.