Sony Tektronix WFM 1125, Руководство по обслуживанию

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Theory of Operation
WFM 1125 Option 0A/0B/0C/0D Service Manual
3-3
With the above features, this device performs interpolation by a factor of 53, that
by a factor of 23, and sampling by a factor of 52/53.
OFFSET operates the UP/DOWN counter through the pulse that is output from
the rotary encode (V-POS knob on front panel). The increase or decrease in the
UP/DOWN counter is read by the CPU. The vertical position is changed by
increasing or decreasing the selected GF9101’s digital offset.
The vertical data is obtained by selecting the data to be output, out of the output
data from the GF9101.
Each time effective data is output from the GF9101, the horizontal data is
obtained by incrementing the internal counter. Digital sweep is implemented as
follows: each time one-line display ends, it is loaded to the value preset for the
counter.
X-RAM and Y-RAM linearly convert the 15-bit wide data from ADDRESS
GENERATOR into 9-bit data. Each of them is a 9-bit wide, 32K-word RAM.
X-RAM is for horizontal conversion, and Y-RAM for vertical conversion.
HISTOGRAM uses the X-RAM and Y-RAM outputs as the addresses. It reads
the data that indicated when the control signal indicating the effective data is
enabled. After adding 1 to that data, HISTOGRAM writes the sum into the same
address.
U450 and U460 constitute one pair, and U480 and U490 the other. Each of these
RAMs can address a data rate against up to once for 4 clocks (37.125 MHz).
While one pair is in Addition mode, the other is in Read mode. The results are
sent to the VARIABLE PERSISTENCE circuit. Mode switching takes place
when the last piece of data of a frame has been written.
The results of HISTOGRAM is written into U510 and U520. VARIABLE
PERSISTENCE reads the results from these two RAMs simultaneously. It then
adds the sum of the two results to the value obtained by multiplying the values
stored in U510 and U520 by a constant. VARIABLE PERSISTENCE writes the
result into the same address as the HISTOGRAM read-out address, again.
If the above constant is 0, VARIABLE PERSISTENCE is set off. If it is 1, the
infinite state is entered.
U555 and U550, used for overlay, display characters and/or divisions in the
whole area (480 x 640) of the VGA display.
OFFSET
ADDRESS GENERATOR
XĆRAM and YĆRAM
HISTOGRAM
VARIABLE PERSISTENCE
VRAM