Commodore Amiga A500 Technical Reference Manual page 82

tween all Expansion Slots. The terms
86 Pin Slot, Coprocessor Slot,
and
Local Slot
are considered synonyms, and pertain t o the 86 pin
Coprocessor Slot in the A2000 and B2000. The terms 86
Pin Edge
and
Expansion Edge
are considered synonyms, and pertain t o the 86
pin Expansion Edge in the A1
000
and A500. The
Local Bus
is the
processor bus directly connected t o the
68000
processor and the
Coprocessor Slot or Expansion Edge; both the Coprocessor Slot and
Expansion Edge are considered Local Bus Ports. Each different im-
plementation of a hardware design is termed an
Instance
of that de-
sign; thus, the A2000's Expansion Bus, the B2000's Expansion Bus.
and all third party ZORRO backplanes for the AI
000
or A500 are in-
stances of the Expansion Bus.
Along with an understanding of Amiga bus terms, a familiarity with
Motorola's
68000
processor and its characteristic names and related
terms will also be very useful in understanding this section.
POWER CONNECTIONS
The Expansion Bus provides several different voltages designed t o
supply expansion devices. The A2000 power supply is a "switching"
power supply, currently rated at 2 0 0 watts, which supplies the main
board and all other expansion ports, as well as the Expansion Bus.
Digital Ground (Ground) Digital supply ground used by all expansion cards as the return path
for all expansion supplies. This is found on all instances of the Expan-
sion Bus. See the Table at the end of this section for pin assignments.
Main Supply
(
+
W)
Main power supply for all expansion cards, and is capable of sourcing
large currents; each Expansion Slot can draw up t o 2.0 Amps of
+
5,
and a single Slot can draw as much as
4
Amps if necessary, for de-
vices such as
8
megabyte RAM cards. The maximum supply current
for the entire A2000 system is 2 0 Amps on the
+
5 supply. All ports
open to the outside of the box have their own, separate
+
5V
supply
that's short protected, thus no loads external to the A2000 box need
be considered. This supply is found on all instances of the Expansion
Bus, though the available currents may vary. Pins: 5 , 6 .
Negative Supply
(
-
W)
Negative version of the main supply, for small current loads only;
there's a total of 0.3 Amp for the entire A2000 system. Found on all
instances of the Expansion Bus, though the available currents may
vary. Pin:
8.