Harris Atlas DVL400, Technical Manual

Page: 104 / 180

4-4 888-2473-001 2/25/03
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation ATLAS Series™
4.3.1 Micro Module
All of the control boards in the transmitter use the 376 Micro Module. The micro
module is a daughter board with a standardised interface which is plugged into a
motherboard. It contains Flash memory for storage of its programming and SRAM
for program execution. The programming in the flash memory can be re-
programmed or upgraded using In-System Programming or ISP (no hardware needs
to be changed) via serial connection. In general the micro modules are responsible
for control, monitoring and reporting, but have very little to do with transmitter
protection which is handled mainly by the CPLDs (see "4.3.2 CPLD, Complex
Programmable Logic Device" on page 4-5).
Features of the 376 module include:
a. Built-in CAN (Controller Area Network) bus controller
b. 16 A/D inputs for analogue metering
c.
A serial EEPROM for non-volatile memory storage
d.
A built in clock running at 4.194MHz which will let the micro run at 16-
25MHz
e.
Power failure detection
f. A watchdog which will reset the micro if it is not triggered at least every 1.6
seconds (this time interval will change depending on the application). A dis-
crete logic device or CPLD is almost always provided on the motherboard to
act as an I/O expansion device and in some cases as life support if the micro
module fails.
g. Multiple I/O lines whose direction of signal flow is based on the flash mem-
ory programming. These could be control or status, inputs or outputs, depend-
ing on the particular use.
The main responsibility of the micro module is control of the CPLD and the
reporting and receiving of information over the CAN bus. This means that the
CPLD will continue to monitor and protect the systems to which it is connected
even if the micro module fails. However, there will be no reporting of information
to the rest of the transmitter system since access to the CAN bus is gone without the
micro module.