16
Ramp Calibration
Ramp Calibration
In order to calibrate the Analog to Digital Conversion, the DSP uses a general-purpose i/o pin to overdrive the
analog VRAWSEN signal present at the comparator input U6200.9 for the duration of a conversion cycle. This
forces the input to +3.3 volts. The bit value read for CPVRAW (U6000.14) becomes the full-scale value. Dividing
this value into the counts obtained on the other inputs, or on future counts obtained on the CPVRAW input
normalizes the counts relative to full scale. This calibration cycle is performed at a regular interval and can be
observed by looking at the VRAWSEN signal. Under normal input line conditions, VRAWSEN will be signifi-
cantly below 3.3 volts except for the calibration cycle, when it will step to 3.3 volts for the duration of the cycle.
Analog
Signal
Converted
Signal
DSP (U7000)
input pin
Use
BEQ+ CPBCP-
113
BEQ- CPBCP+
115
Bass compensation. Wiper position can
be determined by (BEQ+ - BEQ-)/(BEQ+
+ BEQ-).
IVOL
CPVOL
116
Volume control input when the control
module is present
VRAWSEN CPVRAW
117
Use to prevent clipping of power
amplifiers, monitored to determine
excess energy consumption for
transducer DC offset protection.
