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Theory of Operation
2715 Spectrum Analyzer Service Manual
3-57
BCLK
DSPRBQ
DSPGRNT_L
RAMAD<14..0>
RAMD<7..0>
VWFM<7..0>
VDAC<7..0>
0ns 500ns 1000ns 1500ns 2000ns 2500ns 3000ns
HDAC<8..0>
DSBLNK_L
3500ns
Figure 3- 21: The Display of a Single Vector of a Waveform
Figure 3--22 shows the display of a single column of character dots.
BCLK
DSPRBQ
DSPGRNT_L
RAMAD<14..0>
RAMD<7..0>
VWFM<7..0>
VDAC<7..0>
0ns 2500ns 5000ns 7500ns
HDAC<8..0>
DSBLNK_L
Figure 3- 22: A Single Column of Character Dots
Horizontal Output. The Horizontal Output section uses a DAC312 (U41), an
operational amplifier (U45), and DG444 analog switches (U43 and U34), to
generate the DSHOR signal, which is in turned used to deflect the CRT beam on
the Power Supply board. The DAC312 is a twelve bit DAC that, has had its
lower three bits tied to ground to turn it into a nine bit DAC. The DAC receives
data from the Readout LCA (U46), and converts it into a horizontal position on
the screen. The output of the DAC is then converted to a voltage via R95 and
R97. This voltage is then amplified by an MC34001 operational amplifier (U45).
Added to the DAC output is a 3300 pF capacitor, C96. This capacitor is required
to remove the glitch current on the DAC output at major code transitions.
Adjustments for Horizontal Output Gain (HOG), R107, and Horizontal Output