Normally, memory location 54017 contains a 253. By using the BASIC
language POKE
command you can modify this
memory
location to
switch the extra
RAM
. For exampl
e,
POKE
54017, 225 selects the first
section of extra
RAM
and makes that section available to the 6502
chip (but not to the
ANTIC video chip).
The
formula for selecting a bank of memory
in
the 130XE
is
:
POKE
54
OJ. 7
..
253
+
4*ADDRESS
+
J.6*MODE
TABLE
OF
VALUES
ADDRESS
SECTION
OF
MEMORY
0
o to 16383
1
16384 to 32767
2
32768 to 49151
3
49152 to 65535
MODE
6502 ACCESS
ANTIC ACCESS
0
Ext
ra
Ext
ra
1
Normal
Extra
2
Extra
Normal
3
Normal
Normal
MEMORY LOCATION 54017
Bit
#:
7
6 5
4
3 2
1
0
Value:
128 64
32
16
8
4 2
(If set)
? ?
? ?
X
Video CPU Bank
Bank
Bank Bank
MSB LSB
Enable Enable
(VBE) (CBE)
Bits
0,
6,
7, 1 should always be set.
If
VBE
or CBE
is
set, corresponding accessing
is
to normal. If
0,
any
access to address
$4000- $7FFF
is
to the extra set by value
of
bank
bits.
122
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