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adapt to new segments; some other text changes

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git-svn-id: svn://svn.cc65.org/cc65/trunk@4728 b7a2c559-68d2-44c3-8de9-860c34a00d81
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cpg 2010-06-25 23:47:37 +00:00
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commit c992a3596b
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109
doc/atari.sgml
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@ -271,15 +271,15 @@ or f80.com software is missing. Of course you may use stdio.h functions.
<sect1>Function keys<p>
These are defined to be Atari + number key.
Function keys are mapped to Atari + number key.
<sect1>Reserving a memory area inside a program<label id="memhole"><p>
The Atari 130XE maps its additional memory into CPU memory in 16K
chunks at address &dollar;4000 to &dollar;7FFF. One might want to
prevent this memory area from being used by cc65. Other reasons to
prevent the use of some memory area could be the buffers for display
lists and screen memory.
prevent the use of some memory area could be to reserve space for the
buffers for display lists and screen memory.
<p>
The Atari executable format allows holes inside a program, e.g. one
part loads into &dollar;2E00 to &dollar;3FFF, going below the reserved
@ -288,7 +288,9 @@ memory area (assuming a reserved area from &dollar;4000 to
&dollar;BC1F.
<p>
Each load chunk of the executable starts with a 4 byte header which
defines its load address and size.
defines its load address and size. In the following linker scripts
these headers are named HEADER and SECHDR (for the MEMORY layout), and
accordingly NEXEHDR and CHKHDR (for the SEGMENTS layout).
<p>
<sect2>Low code and high data example<p>
Goal: Create an executable with 2 load chunks which doesn't use the
@ -298,14 +300,16 @@ segments should go above &dollar;7FFF.
<p>
The main problem is that the EXE header generated by the cc65 runtime
lib is wrong. It defines a single load chunk with the sizes/addresses
of the LOWCODE, INIT, CODE, RODATA, and DATA segments (the whole user
of the STARTUP, LOWCODE, INIT, CODE, RODATA, and DATA segments (the whole user
program).
<p>
The contents of the EXE header come from the EXEHDR segment, which is
defined in crt0.s. This cannot be changed w/o modifying and
defined in crt0.s. This cannot be changed without modifying and
recompiling the cc65 atari runtime lib. Therefore the original EXE
header must be discarded. It will be replaced by a user created
one.
one. The discarding is done by assigning the EXEHDR segment to the
BANK memory area. The BANK memory area is discarded in the new linker
script (written to file "").
<p>
The user needs to create a customized linker config file which adds
new memory areas and segments to hold the new EXE header and the
@ -314,24 +318,32 @@ needs to be created which defines the contents of the new EXE header
and the second load chunk header.
<p>
<p>
This is a modified cc65 Atari linker configuration file (split.cfg):
This is an example of a modified cc65 Atari linker configuration file
(split.cfg):
<tscreen><verb>
SYMBOLS {
__STACKSIZE__ = $800; # 2K stack
__RESERVED_MEMORY__: value = $0000, weak = yes;
}
FEATURES {
STARTADDRESS: default = $2E00;
}
MEMORY {
ZP: start = $82, size = $7E, type = rw, define = yes;
HEADER: start = $0000, size = $6, file = %O; # first load chunk
RAMLO: start = $2E00, size = $1200, file = %O;
RAMLO: start = %S, size = $4000 - %S, file = %O;
BANK: start = $4000, size = $4000, file = "";
SECHDR: start = $0000, size = $4, file = %O; # second load chunk
RAM: start = $8000, size = $3C20, file = %O; # $3C20: matches upper bound $BC1F
TRAILER: start = $0000, size = $0006, file = %O;
}
SEGMENTS {
EXEHDR: load = BANK, type = ro;
NEXEHDR: load = HEADER, type = ro; # first load chunk
STARTUP: load = RAMLO, type = ro, define = yes;
LOWCODE: load = RAMLO, type = ro, define = yes, optional = yes;
INIT: load = RAMLO, type = ro, optional = yes;
CODE: load = RAMLO, type = ro, define = yes;
@ -340,9 +352,10 @@ SEGMENTS {
RODATA: load = RAM, type = ro, define = yes;
DATA: load = RAM, type = rw, define = yes;
BSS: load = RAM, type = bss, define = yes;
ZPSAVE: load = RAM, type = bss, define = yes;
ZEROPAGE: load = ZP, type = zp;
AUTOSTRT: load = TRAILER, type = ro; # defines program entry point
AUTOSTRT: load = RAM, type = ro; # defines program entry point
}
FEATURES {
CONDES: segment = RODATA,
@ -354,10 +367,6 @@ FEATURES {
label = __DESTRUCTOR_TABLE__,
count = __DESTRUCTOR_COUNT__;
}
SYMBOLS {
__STACKSIZE__ = $800; # 2K stack
__RESERVED_MEMORY__: value = $0, weak = yes;
}
</verb></tscreen>
<p>
@ -366,30 +375,29 @@ It gets loaded with the contents of the old EXEHDR segment. But the
memory area isn't written to the output file. This way the contents of
the EXEHDR segment get discarded.
<p>
The added NEXEHDR segment defines the correct EXE header. It puts only
the CODE segment into load chunk #1 (RAMLO memory area).
The newly added NEXEHDR segment defines the correct EXE header. It
puts the STARTUP, LOWCODE, INIT, and CODE segments, which are the
segments containing only code, into load chunk #1 (RAMLO memory area).
<p>
The header for the second load chunk comes from the new CHKHDR
segment. It puts the RODATA and DATA segments into load chunk #2 (RAM
memory area).
segment. It puts the RODATA, DATA, BSS, and ZPSAVE segments into load
chunk #2 (RAM memory area).
<p>
<p>
The contents of the new NEXEHDR and CHKHDR segments come from this
file (split.s):
<tscreen><verb>
.import __LOWCODE_LOAD__, __BSS_LOAD__, __CODE_SIZE__
.import __CODE_LOAD__, __DATA_LOAD__, __RODATA_LOAD__
.import __CODE_LOAD__, __BSS_LOAD__, __CODE_SIZE__
.import __DATA_LOAD__, __RODATA_LOAD__, __STARTUP_LOAD__
.segment "NEXEHDR"
.word $FFFF ; EXE file magic number
; 1st load chunk
.word __LOWCODE_LOAD__
.word __CODE_LOAD__ + __CODE_SIZE__ - 1
.segment "NEXEHDR"
.word $FFFF
.word __STARTUP_LOAD__
.word __CODE_LOAD__ + __CODE_SIZE__ - 1
.segment "CHKHDR"
; 2nd load chunk (contains with AUTOSTRT in fact a 3rd load chunk)
.word __RODATA_LOAD__
.word __BSS_LOAD__ - 1
.segment "CHKHDR"
.word __RODATA_LOAD__
.word __BSS_LOAD__ - 1
</verb></tscreen>
<p>
Compile with
@ -400,21 +408,27 @@ cl65 -t atari -C split.cfg -o prog.com prog.c split.s
<sect2>Low data and high code example<p>
Goal: Put RODATA and DATA into low memory and LOWCODE, INIT, CODE, BSS
into high memory (split2.cfg):
Goal: Put RODATA and DATA into low memory and STARTUP, LOWCODE, INIT,
CODE, BSS, ZPSAVE into high memory (split2.cfg):
<tscreen><verb>
SYMBOLS {
__STACKSIZE__ = $800; # 2K stack
__RESERVED_MEMORY__: value = $0000, weak = yes;
}
FEATURES {
STARTADDRESS: default = $2E00;
}
MEMORY {
ZP: start = $82, size = $7E, type = rw, define = yes;
HEADER: start = $0000, size = $6, file = %O; # first load chunk
RAMLO: start = $2E00, size = $1200, file = %O;
RAMLO: start = %S, size = $4000 - %S, file = %O;
BANK: start = $4000, size = $4000, file = "";
SECHDR: start = $0000, size = $4, file = %O; # second load chunk
RAM: start = $8000, size = $3C20, file = %O; # $3C20: matches upper bound $BC1F
TRAILER: start = $0000, size = $0006, file = %O;
}
SEGMENTS {
EXEHDR: load = BANK, type = ro; # discarded old EXE header
@ -424,13 +438,14 @@ SEGMENTS {
DATA: load = RAMLO, type = rw, define = yes;
CHKHDR: load = SECHDR, type = ro; # second load chunk
LOWCODE: load = RAM, type = ro, define = yes, optional = yes;
STARTUP: load = RAM, type = ro, define = yes;
INIT: load = RAM, type = ro, optional = yes;
CODE: load = RAM, type = ro, define = yes;
ZPSAVE: load = RAM, type = bss, define = yes;
BSS: load = RAM, type = bss, define = yes;
ZEROPAGE: load = ZP, type = zp;
AUTOSTRT: load = TRAILER, type = ro; # defines program entry point
AUTOSTRT: load = RAM, type = ro; # defines program entry point
}
FEATURES {
CONDES: segment = RODATA,
@ -442,25 +457,21 @@ FEATURES {
label = __DESTRUCTOR_TABLE__,
count = __DESTRUCTOR_COUNT__;
}
SYMBOLS {
__STACKSIZE__ = $800; # 2K stack
__RESERVED_MEMORY__: value = $0, weak = yes;
}
</verb></tscreen>
New contents for NEXEHDR and CHKHDR are needed (split2.s):
<tscreen><verb>
.import __LOWCODE_LOAD__, __BSS_LOAD__, __DATA_SIZE__
.import __DATA_LOAD__, __RODATA_LOAD__
.import __STARTUP_LOAD__, __ZPSAVE_LOAD__, __DATA_SIZE__
.import __DATA_LOAD__, __RODATA_LOAD__
.segment "NEXEHDR"
.word $FFFF
.word __RODATA_LOAD__
.word __DATA_LOAD__ + __DATA_SIZE__ - 1
.segment "NEXEHDR"
.word $FFFF
.word __RODATA_LOAD__
.word __DATA_LOAD__ + __DATA_SIZE__ - 1
.segment "CHKHDR"
.word __LOWCODE_LOAD__
.word __BSS_LOAD__ - 1
.segment "CHKHDR"
.word __STARTUP_LOAD__
.word __ZPSAVE_LOAD__ - 1
</verb></tscreen>
Compile with