Atari 1040STE, Руководство по обслуживанию на месте

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and outputs those levels, then takes bit 1 from each plane and outputs the color from
the palette referenced by those 4 bits, etc.
2.9.3 GSTMCU
GSTMCU provides timing control to the Memory Controller, video output, and
monitorIRF output. VSYNC input to the Memory Controller causes the starting
address of the display memory to be reloaded into the address counter during
vertical blanking. DISPLAY ENABLE (DE) tells the Memory Controller and Video
Shifter that a display line is being scanned and data should be loaded into the Video
Shifter. BLANK shuts off the video output from the Video Shifter during periods when
the scan is not in a displayable part of the screen. VSYNC and HSYNC both go to
the monitor output and RF modulator. These signals synchronize the monitor or TV
vertical and horizontal sweep to the display signal.
2.9.4 Memory Controller
In addition to the inputs from GSTMCU mentioned above, there are two output
control signals associated with video. DCYC strobes data from the display memory
into the Video Shifter. CMPCS (color map select) is active only when changing the
color attributes in the color palettes.
2.9.5 Sound Synthesizer
The YM2149 Programmable Sound Generator (PSG) produced music synthesis,
sound effects, and audio feedback (e.g. alarms and key clicks). The clock input is 2
MHz; the frequency response range is 30 Hz to 125 kHz. There are three sound
channels output from the chip, which are mixed and sent to the monitor speaker.
The PSG is also used in the system for various Il0 functions relating to printer port,
disk drive, and RS232.
2.9.6 Video Interface
The three types of video output interface provided by the STEs are analog RGB and
monochrome, composite and modulated RF. The presence of a monochrome
monitor is detected by the MONOMON input (when a monochrome monitor is
connected, it will be TTL low). The possible displays are:
MONOCHROME:
single emitter follower amplifier driving the output of the Video
Shifter.
RGB: resistor network sums outputs for each color. The three colors each have an
emitter follower amplifier to drive output.
COMPOSITE: the outputs of the emitter followers are input to the modulator box,
where the vertical and horizontal sync signals are added to form the composite
signal.