Caple C871i Bedienungsanleitung PDF herunterladen (Seite 285)

Apple II Computer Info

The IIe has built-in emulation of the "language card" that is used in

an Apple ][ or ][+ to increase the total memory to 64K.

The language card provides 16K of additional RAM that is bank-switched

into the $D000-$FFFF area, which is normally occupied by the firmware

(Applesoft BASIC and the monitor firmware). This is only 12K of

address space: the extra 4K is provided via a second bank at $D000-$DFFF.

In a 128K IIe, the language card structure is repeated in both main

and auxiliary memory, and the same soft switches control both banks.

The active bank is controlled by the ALTZP soft switch (described

earlier).

The language card soft-switches are as follows. Note that they are

the same for a ][ or ][+ with a language card in slot 0, except that

the "read" locations are not available. An Applesoft/Integer BASIC

ROM card uses a subset of these locations (it only supports

$C080/$C081).

All of these soft switches may be controlled with a read or write

access. They control which areas are accessed for subsequent read and

write operations in the $D000-$FFFF. "bank 1" and "bank 2" refer to

the two alternative 4K RAM banks at $D000-$DFFF. $E000-$FFFF accesses

the same memory area no matter which bank is selected.

Name Location Read Write

LC2RD $C080 RAM, bank 2 -

LC2WR $C081 ROM RAM, bank 2 (see below)

ROMONLY2 $C082 ROM -

LC2RW $C083 RAM, bank 2 RAM, bank 2 (see below)

LC1RD $C088 RAM, bank 1 -

LC1WR $C089 ROM RAM, bank 1 (see below)

ROMONLY1 $C08A ROM -

LC1RW $C08B RAM, bank 1 RAM, bank 1 (see below)

In summary:

$C082 or $C08A totally disables the language card RAM. The ROM is

enabled for read, and the RAM is completely disabled. The two

locations are identical in function.

$C080 or $C088 enables the language card RAM in "write protected" mode

(acting as a ROM). This is used by DOS 3.3 when Integer BASIC is

loaded into the language card. The two locations select different 4K

RAM banks in the $D000-$DFFF area.

$C081 or $C089 enables the language card RAM in "write only" mode,

with the ROM enabled for read operations. This is used when executing

code in ROM, but allowing data to be copied into the language card

(e.g. when copying parts of the ROM into the language card). The two

locations select different RAM banks in the $D000-$DFFF area.

$C083 or $C08B enables the language card RAM in "read/write" mode,

with the ROM completely disabled. This is used when exeucting an

operating system (e.g. ProDOS or Pascal) from the language card space,

where part of the RAM is used as buffering memory, for example. The two

locations select different RAM banks in the $D000-$DFFF area.

Apple II Computer Technical Information : Apple II Family Hardware Info

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