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GE Grid Solutions
• Inter-task communication and synchronization controlled from an efficient dedicated
functional group
• Dynamic memory allocation and reclamation, using an enhanced, highly efficient, first-fit
algorithm
• Real-time clock control managed via a service call from an external time base. The real-time
clock:
− Maintains calendar time
− Performs time slicing, which allows processes to pause
− Supplies a time-out option to other service calls
• Direct memory access support is not required
• Efficient real-time responsiveness
Boot-Up Code
The D20 system initializes from the BootROM. It checks and verifies the contents of the
BootROM, then initializes the system hardware and various I/O devices. If it finds any errors or
defects in the memory, the system either shuts down to a minimum running state or, in the event
of serious defects, shuts down completely.
After the initial diagnostic routines are run, the boot-up code downloads the operating system
code into RAM so that it can be accessed more quickly. From this point on, all resident firmware
and supplied custom applications run from either 32-bit wide RAM or 32-bit wide flash. The
system and application databases are stored in NVRAM.
Device Drivers
The D20 uses two communication device drivers:
• Octart serial I/O chip, which manages input and output through eight serial ports.
• HDLC controller chip (dual-port), which forms part of the high-speed D.20 Link between
the D20ME and the D20 I/O peripherals.
68K Monitor Functions
Monitor functions include debugging tools that users can access via a PC, VT100 terminal with a
keyboard, or remotely via telnet. Monitor functions include memory examination, dumping and
editing, setting break points, single-step modes, communication port loop-back tests, mark and
space modem adjustments, and CPU usage and process profiling.
Watchdog Task
Watchdog is a simple, low-priority task that is designed to send a reset signal to the
watchdog timer circuit. As long as this circuit is reset every second, the system will not be
rebooted. The D20 performs standard self-checks on initial start-up, periodically during
operation, and as manually requested through WESMAINT.
GE Information
D20/D200 Technical Overview
PRPI-019-3.00-10
33
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