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Appendix A
The ROM is configurable in size (128 to 512 k-words), uses Flash or
EPROM, and is typically factory set to 512 k-words Flash. The RAM is
supplied by VDD2, which provides non-volatility, as long as either a DC
power, or mains is supplying the ADFM, that is the RAM contents is main-
tained during the sleep mode (power down mode). RAM contents are lost
if none of these sources are present.
The RTC keeps time and date, including leap year. When the RTC's pro-
grammed alarm compares with the current time and date, its alarm function
generates an interrupt, which in turn wakes the CPU up from an asleep
mode (power down mode). It also keeps time for time between ensembles
and time between pings for example. The RTC's memory is backed up by a
250-mAh Lithium coin cell for up to 3 years, even if external and internal
power sources are not present. However, it is recommended to change the
backup battery at least every 2 years.
The address decoder provides all enables and controls for all CPU func-
tions, bus interface enable, timing generator enable and control, receiver
enable and control, off-board enable and control (serial interfaces such as
RS-422, RS-232), and power supply controls. Interrupt priority encoding
and bus-ready control (wait state generator) are also functions of the de-
coder.
The CPU supervisor monitors power, and generates an un-maskable inter-
rupt for the MPU to signal a power fail. The CPU is able to shut down in a
controlled manner. If the supply voltage should fall any further, the super-
visor generates a system reset. Further more, it protects RAM and RTC
from an erroneous writes during power down or power fail events. When
the system is in sleep mode a RTC interrupt sets a supervisor register,
which in turn switches the main 5 volt power on (VDD1). The MPU is able
to interrogate the source of the interrupt, and will proceed according its in-
structions.
The CPU interfaces to the system bus through bi-directional digital bus
transceivers. Since all of the functional modules are isolated by these trans-
ceivers (as described above), fault isolation of this complex system is pos-
sible; it would be very difficult, if not impossible in an un-isolated bused
system.
A-2.5
User Interface
Several user interfaces are integrated into the ADFM. In particular these are
a RS-232 serial data interface, a 9600 baud data Modem, and a LCD dis-
play. A solid state recorder is also built into the ADFM. The Modem and
serial interface allows the operation of the ADFM without restrictions.
However, the host terminal or host computer must be able to send a Break
page A-4
MGD Technologies, Inc.
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