Apple Logic Board Información técnica descargar pdf (Pagina 32)

In general the values represent the following:

A. FUNCTION. The first value identifies the function to be

performed. This must be an integer in the range 0 to 14.

B. SEGMENT NAME. The second value gives the name of the RAM

segment to use. (values: integer 1 — 32,767)

C. ERROR STATUS. The third value must be a variable name.

RAMEXPAND will store a status value in the variable upon comp-

letion of the function. This can be used to determine if the

function was performed successfully.

START. The fourth value depends upon the particular

function. It may represent the start of a program area, or an

array name.

E. END. The fifth value also depends upon the particular

function. It may represent the end of a program area.

C. CALLING RAMEXPAND

RAMEXPAND is called from BASIC programs using the CALL

statement. Since locations 10 — 12 ($A — $C) are set to point to

RAMEXPAND, a CALL 10 statement and in Applesoft the USR function

both serve to call RAMEXPAND.

Thus, in summary, in order to execute a RAMEXPAND command,

the command string CM$ is first set up, and then RAMEXPAND is

called through a CALL 10, etc. This process is repeated for each

command to be executed.

0. INITIALIZING RAMEXPAND

After RAMEXPAND has been installed (see previous section,

INSTALLING RAMEXPAND), it must be initialized. This is

accomplished through the RAMEXPAND initialization function

(function code = 14). The command string to initialize RAMEXPAND

is as follows:

CM$ = “14,0,A,0,0”

where A = error status variable.

E. ATTACHING MEMORY BLOCKS

Following initialization, the extended RAM memory to be used

by RANlEXPAND should be specified. The connect function (#9) is

used to attach blocks of memory to the system by indicating to

RAMEXPAND which blocks of memory are to be used in a particular

expansion RAM board (Saturn 32K, 64K, 128 RAM Board or 16K RAM

board). This function can be used to “attach” a single block of

memory or multiple blocks of memory within a given expansion

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Apple Logic Board Información técnica Pagina 32