Table of Contents
Advertisement
Issue the command:
dp 20,0,2,0,12
Within 500msec, expect the response:
DSPkexxxxxxxx
>
where "xxxxxxxx" is a text string which encodes the signal strengths measured at he input.
Take, for instance, the string:
EF2BEE2A
Break this last 8-character response into four 2-character hex numbers, e.g., "EF2BEE2A"
becomes "EF 2B EE 2A". These four numbers, read from left to right, are the figures for
left_distortion, left_signal, right distortion, and right_signal.
Convert these four numbers from hex to decimal: "EF 2B EE 2A" becomes -17, 43
-18, 42.
Subtract 45 from each of these numbers: "-17 43 -18 42" becomes -62, -2, -63, -3. The
units are now in dB referenced to the PCBs full-scale input of 2Vrms.
3.12.1 L distortion:
3.12.2 L signal:
3.12.3 R distortion:
3.12.4 R signal:
Measurement notes:
a)
The "f6" in the "tn 5" command above is the programmed output volume.
b)
"f6" = -10 in 8-bit signed hex numbers.
c)
-10dB below the pcbs full scale output of 6Vrms is 1.9Vrms.
d)
Loading the PCBs output signal (500W output impedance) with the PCBs input imped-
ance drops the signal at the input to about 1.6Vrms.
e)
1.6Vrms is about -2dB below the pcbs full-scale input of 2Vrms. Thus, expect signal
measurements of about -2dB.
Due to the limited precision of the math used in the calculation, very small numbers (e.g.,
the distortion measurement) will sometimes get rounded to "0x80", or minus full-scale.
This is not an error; think of it more as "negative infinity".
Framingham, MA 01701-9168
-45dB (max.)
-4dB (min.)
-45dB (max.)
-4dB (min.)
SIZE
FSCM
CLASS
A
32108
0-dB (max.)
0-dB (max.)
DWG NO.
TS
264695
SHEET
REV.
46
00
12 of 16
Advertisement
Table of Contents
