-3 color bits coming from the WXR board in the DMC, via three digital serial lines (8 Mbits/s per line)
-1 clock signal used to fetch the WXR color bits (8MHz). Outputs:
-2 analog outputs for the spot position (X and Y)
-3 analog outputs for RGB video. Inputs/outputs:
-Dedicated serial link with the DMC (800 Kbit/s) : DSDL.
(b) Description (Ref. Fig. 020) The SG can be divided in several functional blocks :
1_ Processor Chip and Computation Chips
Three VLSI circuits are the "heart" of the SG. These 3 chips
constitute a very powerful programmable graphic processor
whose principal function is to control the spot position, the
drawing speed and the blanking according to the commands of
the drawing program. They give a new spot position every 500
ns (2 MHz).
2_ Sine/cosine Memory
These 2x(4Kx12) PROMs convert the angle delivered by the
Processor chip in two increments for the X and Y computation
chips. For each angle value theta, this memory contains ; sin
theta, cos theta, 0.075 sin theta.
This allows the number of drawing speeds available to be
doubled artificially (16 instead of 8).
This device allows the speed to be adjusted in order to
optimize power consumption.
3_ Interpolator
The two functions of this LSI circuit designed in HCMOS
technology are:
- to demultiplex the 2 x 6 bit outputs of the computation
chips in 12 bits, in order to drive the Digital to Analog
Conversion
- to compute, according to the two last values given by the
computation chips, 3 intermediate positions of the spot in
500 ns period. This interpolation allows the exact position
of the spot to be known every 125 ns and consequently to be
able to change the color or the blanking signal with more
precision in order to improve drawing quality.
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Symbol Generator - Block Diagram
Figure 020
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4
_
5
_
6
_
Digital/Analog Converters Two identical hybrid circuits (one for each way) are used for the digital to analog conversion, sampling and smoothing of the spot position signals.
Masks (Ref. Fig. 021) This circuit is able to furnish for each of the two masks a signal indicating if the spot is in or out of the mask. The accuracy of this indication is 125 ns thanks to the precise position given by the interpolator. The limits of the masks are contained in a RAM and consequently can be easily modified. The drawing of the mask limits is done by the SG itself.
-The SG has 2 identical external masks in addition to the 2 internal windows of the processor and computation chips. The output signals of the external window circuits can be used as a blanking signal or to change the color.
Color control
(Ref. Fig. 022)
The functions of this LSI circuit are :
-
to change the color according to the program commands
-
to switch the color according to the color choice bits which can be internal window or mask signals
-
to multiplex the color bits coming from the SG and those coming from the WXR
-
to program a delay on the color bits to provide adaptability between digital and analog circuits taking into account devices dispersion.
Only 3 WXR inputs are used in the CRT, and 5 outputs provided. 4 color codes can be stored in 4 registers. This permits either to change normally the color by software or to switch in real time among the possibilities according to the color choice bits.
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Mask Circuit - Block Diagram
Figure 021
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Color Circuit Block Diagram
Figure 022
R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 31-63-00Page 66 1201-299, 301-302, 1Config-1 May 01/05 1 1 1CES 1 The available colors are presented on the following table. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：A320飞机维护手册 AMM 指示/记录系统 7(134)
