Ceilometer CT25K
User’s Guide CT25K-U059en-2.1
64
The DMC50B Processor Board is the central processing unit of the CT25K. It
performs the following functions:
- A-to-D conversion of signals from various internal sensors
- Data processing under a powerful real-time operating system
- Serial communication with external devices
- Internal subassembly control
- Built-in tests of the whole system
Processor
The DMC50B has a fully static 16-bit CMOS processor type 80C188EB. This
processor is especially designed for very low power applications and it can be
switched by software to its low power idle mode between tasks.
FLASH EEPROM memory is used as storage for the real-time operating
system and application specific code files. The SRAM memory stores the
variables and serves as an intermediate database.
A Watchdog timer is employed to assure a complete system reset in the event
of system malfunction.
A-to-D Converter
Analog data is digitized by a fast ± 12 bit A-to-D Converter located on the
DMC50B Board. The converted data is analyzed by the processor and used for
various purposes, e.g. internal monitoring.
Serial Communication Ports
A UART (Universal Asynchronous Receiver-Transmitter) controls the serial
communication of the system. The CT25K provides two serial communication
ports, "MAINTENANCE" (external connector J4, Line/Port A at Processor
Board) and "DATA" (external connector J3, Line/Port B at Processor Board).
Port B is intended to be used for measurement data communication and Port A
for on-site maintenance. When desired, port settings can be changed by
corresponding software commands (paragraphs 3.4 and 4.3 for more
information). The communication to the DC Converter DPS52 is carried out
by I
2
C Bus, and to the Interface Board DCT51 by I
2
C Bus and by address and
data busses.
The DMC50B Processor Board is built using surface mount technology on both
sides, and has no jumpers or IC sockets. The DMC50B is conformal coated for
harsh conditions; its temperature range extends from -50 °C to +70 °C.
The DMC50B external communication connectors are located on the front
edge of the processor board. The cables can be disconnected for maintenance.
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