Harris Atlas DVL400, Техническое руководство

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2/25/03 888-2473-001 4-5
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
ATLAS Series™
4.3.2 CPLD, Complex Programmable Logic Device
The transmitter control boards with the micro module also incorporate a CPLD
(Complex Programmable Logic Device) with the exception of the module
controllers. The CPLD is not a microprocessor but is actually just programmed
discrete logic and is therefore very stable and reliable. The CPLDs in the transmitter
perform two vital functions in terms of control and transmitter monitoring:
a.
I/O Expansion
b.
Life Support Backup
4.3.2.1 I/O Expansion
Each Micro Module only has a limited number of Input/Output or I/O lines
available. The CPLDs provide a way to easily expand the available I/O ports on
each control board. Basically, the CPLDs are actually controlling and monitoring
the I/O for each control board. The micro module is taking that information and
relaying it, via the CAN bus, to the Main Controller for display on the front panel
control screen or a remote control system. If the micro module wants to send a
control command, it simply addresses the correct I/O line on the CPLD and it then
sends out the command.
4.3.2.2 Life Support Backup
The CPLD monitors the watchdog circuit or more specifically the RESET line on
the micro module. If the micro module stops executing its programming, the
watchdog circuit will activate the micro reset line and the control board in question
is considered to be in "Life Support Mode". Since all metering and status is done via
the CAN bus, the CPLD will still monitor and protect the systems to which it is
connected, but there will be no information reporting to the rest of the control
system, the front panel display or a remote control. Control and protection are now
limited to the hardwired control lines on the system control bus and any protection
circuits built into the CPLD or the control board itself.
For more information on specific functionality of each control board in a life
support mode, see the individual control board descriptions later in this section.