Crown Audio IQ-P.I.P.-MEM - Manual (Page 29)

Page 29 Reference Manual
IQ–P.I.P.-MEM Programmable Input Processor for IQ Systems
tally controlled attenuator. Follow-
ing the attenuator, the signals pass
through a final output buffer stage,
which also can invert the polarity of
the signal when required. The au-
dio signal is then fed through the
PIP edge card connector and into
the amplifier.
5.2 Amplifier Monitoring:
“Monitor Inputs”
The IQ–P.I.P.-MEM can monitor the
status of the amplifier using a num-
ber of “monitor inputs.” There are
two types of signals—audio and
status. The audio signals that are
monitored are the input to the PIP
and the output of the amplifier.
These signals enter the PIP and are
fed into a precision peak detector
which insures that instantaneous
signal peaks are not “missed” by
the PIP The detector outputs are
then fed through a multiplexer into
a logarithmic conversion circuit for
dynamic range scaling. The output
of this circuit is then fed into the A/
D converter on the microprocessor,
where the signal is converted and
sent to the host computer via the
Crown Bus.The status signals that
are monitored are ODEP level, IOC
status and VCC status. These sig-
nals enter the PIP, pass through a
buffer stage, and are fed into the A/
D converter on the microprocessor.
The signals are then converted and
sent to the host computer via the
Crown Bus.
5.3 Amplifier Control
The IQ–P.I.P.-MEM can control the
following functions: audio level, au-
dio polarity, high-voltage power
supplies, DSPI and the AUX port.
These functions are controlled us-
ing ports on the microprocessor
and some external support cir-
cuitry. The audio level is controlled
by the microprocessor through a
digitally controlled analog attenua-
tor. The DSPI LED flashes when-
ever a valid IQ command has been
received and can be forced to stay
on to facilitate diagnosis of Crown
Bus wiring problems.
5.4 IQ System Communica-
tions
The IQ–P.I.P.-MEM communicates
with the host computer via the
Crown Bus. Connections to the
Crown Bus are made via the 4 and
5-pin locking DIN connectors on
the rear panel. IQ commands enter-
ing the PIP are fed into an input re-
ceiver circuit that converts the 20
mA current loop signal into a stan-
dard logic signal that the micropro-
cessor can understand. This signal
is also passed directly to the Crown
Bus for output where it is passed on
to the remainder of the loop. Data
sent in response to IQ commands
is also sent through the Crown Bus
output where it passes through the
remainder of the loop and back to
the host computer. A “drop out” re-
lay is also present which makes a
physical contact between the
Crown Bus input and output con-
nectors in the event of a power fail-
ure. This means that as long as the
Crown Bus cables are connected to
the PIP, the Crown Bus will remain
unbroken—even if power to the PIP
is lost.
5.5 Microprocessor and
Reset Switch
The “brains” of the IQ–P.I.P.-MEM
are contained in the microproces-