Pdev configuration guide

02feb07

    This page holds current measurements for the  voltage/power level settings for the pdev spectrometer. The settings path is:
 
function V/P Shift
Bits
Bits Sat notes
A/D sample V
12 Adc
Ovf

PolyFilter/ffts V
18
19 bits arithemetic.
Pshift V Down 18 fft
Ovf
13 bits mask. Each bitdown shifts after a butter fly stage.
B0 last butterfly(size2). B12 first butter fly stage.
Shift
Vshift
V 3Up 32 Vsh
Sat
After fft before stokes upshift values.
Compute pwr P
32

Dshift P 4Dwn 32
down shift prior to accumulation. 
Accumulation P
40 Acc
Sat
accumulate in 40 bit numbers. Assume 32 bit input placed in lower 32 bits of accumulator
Ashift P 3Up 32 Ash
Sat
uppper most 32 bits of accumulator are up shifted in 32 bit word. This is needed for packing 8 or 16 bits.

 


Testing the different setting for PFB saturation/underflow.

 
minimum Pfb shift for no pfbOverFlow vs a/d levels ( if2noise source)
A/D
Lvls
Pshift pfbOvr
L,H
VSh Dsh Ash Spc
Med
Notes
11,10 0x1800
0x1a00
0,3
0,0
0 0 0
need >=3 shifts
26,22 0x1300
0x0013
0x1600
0,0
12,7
0,0
0 0 0
need >=3 shifts
47,40 0x1600
0x1700
7,8
0,0
0 0 0
need >=4 shifts

 

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