Honeywell UMC800 - Manual (Page 60)

Operation
Power Up / Power Down
52 UMC800 Controller Installation and User Guide Release F
4/01
Operation
Power Up / Power Down
Power-up
A sequence of checks are performed by the controller anytime power is applied to the controller. These
checks are a set of internal diagnostics that are completed in less than 10 seconds after power up and verify
the integrity of the controller hardware, the configuration database and firmware. Communication between
the operator interface and controller is established automatically after these checks are completed. All
outputs are OFF until addressed by the CPU.
Two start up routines are used for initializing the controller configuration.
A warm start is the default routine that is used to restart the controller operation. A warm start begins the
scan cycle of data points using all dynamic data retained from the previous legitimate scan.
A cold start (New start) initializes all control functions to their default initial state, (if default output
values are defined in the configuration). If defined, these values are used as the starting values for
controller operation.
Status indicators on the CPU module consist of four LEDs that indicate normal operation and diagnostic
fault conditions. See Status Indicators (page 59).
When power is applied to the controller, it will power up and initialize to the mode determined by the mode
switch setting on the CPU. See Mode control (page 53) for further information.
Power-down
The controller does not require the configuration to be reloaded when power is restored after a power loss
or power down. During a power interruption, the controller configuration is maintained in battery-backed
RAM and a flash PROM on the CPU module. When the controller power is restored, and provided that the
battery power to the CPU RAM is not interrupted, the controller will perform a warm start. However, if
battery power to the RAM is interrupted, the controller configuration (which was last stored in the flash
PROM on the CPU), will be restored to the RAM when controller power is restored and then the controller
will perform a cold start.
CAUTION
Controller configuration is stored in RAM as well as the flash PROM on the CPU. However, if
you make changes to the configuration while the controller is in Run mode, the changes are
stored in RAM and not in the flash PROM. Therefore, if battery power is interrupted to RAM
during a power down condition, the configuration changes will be lost since controller
configuration will be restored from flash PROM.
Also, the real time clock will need to be set if battery power is interrupted during a power down
condition.