Topic       : Pure Assembler Documentation
Author      : John Kormylo
Version     : PASM.HYP 1.0
Subject     : Documentation/Pure Assembler
Nodes       : 740
Index Size  : 20262
HCP-Version : 3
Compiled on : Atari
@charset    : atarist
@lang       : en
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@help       : Help
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View Ref-File[ Pure C Linkage ]

Functions are called using BSR or JSR instructions which store
the return address on the stack.  When the function is done, it uses
the RTS instruction to resume execution in the calling routine.

Function names and global variables can be defined using GLOBL,
EXPORT, IMPORT, XDEF and/or XREF directives.  Parameters are
passed in registers and/or on the stack (see Parameter Passing).

One can write assembly language functions to be called from Pure C
(see Functions) and one can call Pure C Functions from assembly
language (see Calling).

One can also call TOS functions in ROM directly using the TRAP
instruction instead of calling the interface functions in PCTOSLIB.
TOS functions expect all arguments to be passed on the stack.

One can write entire programs in assembly language and bypass PCSTART
altogether.  The first executable instruction of the first object
module in the project file will be executed first when the program is
run.  At run time, all of RAM will be reserved and A7 will point to
the top of this area.  One should therefore allocate a smaller region
for the program and stack using Mshrink.  One will need information
from BASPAG for this.

Finally, one can insert function addresses into system jump vectors
(see Atari Memory Map) or into exception vectors.  This should
only be done by a program run from the 'AUTO' folder.  These functions
will be executed in Supervisor Mode.

Examples:
  Tversion
  dble_vector_prod
  force_media_change
  auto_resident