Commodore Amiga A1000, Hardware Reference Manual

Page: 264 / 380

The transmission of the start bit is independent of the contents of this register. One start
bit is automatically generated before the first data bit (bit 0) is sent.
Writing this register starts the data transmission. If this register is written with all zeros,
no data transmission is initiated.
DISPLAY OUTPUT CONNECTIONS
All Amiga’s provide a 23-pin connector on the back. This jack contains video outputs and
inputs for external genlock devices. Two separate type of RGB video are available on the
connector
o RGB Monitors ("analog RGB"). Provides four outputs; Red (R), Green (G), Blue (B), and
Sync (S). They can generate up to 4,096 different colors on-screen simultaneously using
the circuitry presently available on the Amiga.
o Digital RGB Monitors. Provides four outputs, distinct from those shown above, named
Red (R), Green (G), Blue (B), Half-Intensity (I), and Sync (S). All output levels are logic
levels (0 or 1). On some monitors these outputs allow up to 15 possible color
combinations, where the values 0000 and 0001 map to the same output value (Half
intensity with no color present is the same as full intensity, no color). Some monitors
arbitrarily map the 16 combinations to 16 arbitrary colors.
Note that the sync signals from the Amiga are unbuffered. For use with any device that
presents a heavy load on the sync outputs, external buffers will be required.
The Amiga 500 and 2000 provide a full-band width monochrome video jack for use with
inexpensive monochrome monitors. The Amiga colors are combined into intensities based
on the following Table:
Red Green Blue
30% 60% 10%
The Amiga 1000 provides an RF modulator jack. An adapter is available that allows the
Amiga to use a television set for display. Stereo sound is available on the jack, but will
generally be combined into non-aural sound for the TV set.
The Amiga 1000 provides a color composite video jack. This is suitable for recording
directly with a VCR, but the output is not broadcast quality. For use on a monochrome
monitor, the color information often has undesired effects; careful color selection or a
modification to the internal circuitry can improve the results. High quality composite
adaptors for the A500, A1000, and A2000 plug into the 23 pin RGB port.
The Amiga 2000 provides a special "video slot" that contains many more signals than are
available elsewhere: all the 23-pin RGB port signals, the unencoded digital video, light
pen, power, audio, colorburst, pixel switch, sync, clock signals, etc.
- Interface Hardware 255 –