Chapter 3 ______________________________________________________ Functional Description
VAISALA _______________________________________________________________________ 11
of the time in the preceding 200 ms period, otherwise the status is
determined as idle.
The current line status is used to lock the switch controls at the time
when the first rising edge is received in RXD1 line at D1/20. Switches
1, 2, and 4 are left open if the line status is "externally driven". In this
case the system uses external receiver and MRG112 is left
unconnected. In the opposite case switches are closed and system
starts communicate with MRG112. Switch 3 is always opened at the
time of switch locking. The locked switch settings are permanent until
next power-up or reset.
The analog switch A2 is of a fault-protected type, where voltage levels
at the protected side pins (3,14,11,6) can exceed the operating
voltages up to +/- 36 V. When operating voltage is exceeded the
protected right side pin enters a protective high impedance state and if
the switch is closed the left side pin connects corresponding operating
voltage level to the pin with a current of up to 10 mA.
LED Lamp Operation
The bicolor STATUS LED lamp V4 shows the status of MRG112
unit. It is controlled by signals STLRED# and STLGRN# . The lamp
is red (STLRED# = 0), green (STLGRN# = 0), yellow (STLRED#
=0, STLGRN# = 0) or dark (both controls inactive).
During active reset V4 is yellow, after reset the lamp is flashing green
until serial line switch is set for external or internal operation. Internal
operation is indicated by solid green and external operation is
indicated by yellow.
The bicolor SVs (Satellite Vehicles) LED lamp V7 indicates the
operation of the GPS Processor. It is controlled by signals SVLRED#
and SVLGRN# . The lamp is red (SVLRED# = 0), green (SVLGRN#
= 0), yellow (SVLRED# =0, SVLGRN# = 0) or dark (both controls
inactive).
During active reset V7 is yellow, after reset the lamp is controlled
directly by signals REDLED and GRNLED from GPS Module, only
the red color is converted as yellow in PLD. The yellow flashing
indicates that the GPS Module is operating and the number of green
flashes between yellow ones are indicating the satellites tracked by
GPS Module. If serial line switch is set for external operation the V4
lamp color is set as solid yellow.
