Commodore Amiga A500 Technical Reference Manual page 108

High Voltage Supply
Higher voltage supply, intended for small loading only; there's a total
( +
12v)
of
8
Amps for the entire A2000 system, much of which is normally
devoted to floppy and hard disk drive motors. Pin: 10.
CLOCK SIGNALS
These are various clock signals useful for synchronous timing of vid-
eo peripherals.
/C1 Clock
/C4 Clock
For NTSC, this is a 3.58 MHz clock that's synched t o the falling edge
of the 7.1
6
MHz system clock. Also known as JCCK in some places.
Pin
34.
For PAL, these frequencies are 3.55 MHz and 7.09 MHz re-
spectively.
For NTSC, this is a 3.58 MHz clock that's synched t o the rising edge
of the 7.1
6
MHz CDAC clock. Pin 19. Again, for PAL, these frequen-
cies are
3.55
MHz and 7.09 MHz respectively.
External Clock (XCLK,
/ The video slot provides for an external system clock, generally used
XCLKN)
t o cause the entire A2000 system t o become synchronized t o some-
thing external. This should be something very close t o the 28.64
MHz clock normally used to drive the system; the value used for
XCLK can be a somewhat higher frequency, although anything too
high will cause memory and other system timings t o break down.
XCLK will only be engaged as the system clock when IXCLKEN is as-
serted. XCLK is found on pin
33.
JXCLKEN
is
on pin 16. There is no
fixed phase relationship between XCLK and internal clocks and video
outputs. Video interfaces must synchronize t o the output clocks1
video.
VIDEO SIGNALS
Analog Video
Digital Video
The main point of this slot is access t o the video signals generated by
the Amiga's custom video chips. Most of these are also found on the
23 pin external video connector.
This is the analog RGB output, which consists of Red, Green, and
Blue signals, each of which generates a 0.7V p-p. 4 7 Ohm terminated
analog output. Found, respectively, on pins 7, I l , and 15.
These signals serve as digital output, suitable for use with an IBM or
Commodore 1 2 8 style
4
bit digital color or monochrome monitor
or similar output device. On the B2000, these (in conjunction with