After Sales
Technical Documentation
RAE/RAK–1N
PDA Hardware
Page 6 – 21
Original, 08/96
Battery charge level limits on CMT and PDA
Figure 5 (overleaf) shows an example of combined CMT and PDA critical
battery levels, measurement accuracy (+/– 50mV). There are two kind of
limits most of which are implemented in software.
The AD converter, located in the CMT module, is used as a source for
battery level values needed by both CMT and PDA software. PDA gets
battery level information from the AD converter via ECI messages. The
CMT HW limit, PDA HW cut–off and Battery protect circuit cut–off are
implemented in hardware and actions are taken without notice to any
software.
The following limits are based on battery level values read from the AD
converter; decisions are made by software.
Battery low level warning 1
If CMT is ON this warning is generated by
CMT sending a message to PDA when warning 1 is
triggered. If CMT is OFF, PDA must generate this
warning itself.
CMT battery cut–off
CMT switches itself off when battery level has fallen
below this level.
Battery low level warning 2
PDA generates this warning when the battery level
value read from CMT has fallen below this level.
PDA limit (Data save)
PDA saves all user data and disables PDA when
the battery level is below this level.
The following limits are implemented in hardware:
CMT HW limit
CMT power supply switches itself off.
PDA HW cut–off
PDA power supply switches itself off.
Battery protect circuit cut–off
A circuit in the battery package switches power off
from battery output pads.
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