Commodore Amiga A500 Technical Reference Manual page 110

POWER CONNECTIONS
The Extended Video Slot provides several different voltages designed
t o supply Video devices. The A2000 power supply is currently rated
at 2 0 0 Watts, which supplies the main board and all other expansion
ports as well as the Video Slot.
Digita Wideo Ground These pins provide additional grounding for digital or video based
(GROUND)
devices. Pins
1,
5,
9,
12, 22, and 32.
Audio Ground
CLOCK SIGNALS
CDAC Clock
/C3 Clock
Timer Time Base
(TBASE)
VIDEO SlGNALS
Composite Video
These pins provide grounding in common with the separate on-
board audio ground. Pins 34,36.
These are various clock signals useful for synchronous timing of vid-
eo peripherals.
For NTSC, this is a 7.1
6
MHz clock that leads the 7.1 6 MHz system
clock by about 70ns (90 degrees). Pin 15. For a PAL system, this
is
7.09
MHz.
For NTSC, this is a 3.58 MHz clock that's synched t o the rising edge
of the 7.1
6
MHz system clock. Also known as
/CCKQ
in some places.
Pin 17. For a PAL system, this is 3.55 MHz.
This is the real time clock time-base input, either 50Hz o r 60Hz, de-
pending on the country involved and the setting of the Time Base
Jumper. The jumper can select either line frequency o r vertical syn-
chronization as the clock's time base. Pin 14.
The main point of this slot
is
access t o more of the video signals gen-
erated by the Amiga's custom video chips. Most of the signals avail-
able here aren't available on any external port.
This
is
the analog level monochrome Composite Video signal also
available on the Composite Video jack of the B2000. Pin 13.