External Disk Connector Defined Identifications
$0000 0000
-
no drive present
SFFFF FFFF
-
Amiga standard 3.25 diskette
$5555
5555
-
48
TPI double density double sided
As
with other peripheral
ID'S,
users should con-
tact Commodore Technical Support for
ID
Assign-
ment.
The serial input data is active low and must there-
fore be inverted to be consistent with the above
table.
External Disk Connector Limitations
1. The total cable length including daisy chaining
must not exceed
1
meter.
2.
A
maximum of
3
external devices may reside
on this interface (2 for the
A2000).
3. Each device must provide a 1000 Ohm pullup
resistor on every open collector input.
Full BUS Termination
Unlike the A1
000
and the
A500,
both versions of the Amiga 2000
have an internal expansion bus, as a function of having an internal
card cage.
Internal
RAM
Expansion
On the
A500,
memory at $C00000 is "slow"
RAM
(the processor is
on the
MOO
locked out by the custom chips) rather than fast
RAM
as suggested
by A1 000 external expansion. Thus, when
ExecBase is transferred to
$C00000 to free up chip
RAM,
there is no speed advantage. Howev-
er, you would still be making real chip RAM available for other pur-
poses. The B2000 functions as the
A500
does in this regard.
EIA
Ring Indicate
Support
The
A500,
A2000 and B2000 support the RS232
RI
lead to allow
operation with modem standards. When the
RI
signal is asserted, the
parallel port SEL line will be driven low.
If
this function is not de-
sired, the
RI
lead should be disconnected in the modem cable.
To Next Page
Loading...
