mirror of https://github.com/hsoft/collapseos.git
Add memory maps
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Virgil Dupras
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@ -89,6 +89,8 @@ I' -- n Copy RS second item to PS
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J -- n Copy RS third item to PS
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*** Memory ***
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(mmap*) -- a Address of active memory mapper. 0 for none. See
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"Memory maps" in notes.txt.
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@ a -- n Set n to value at address a
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! n a -- Store n in address a
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? a -- Print value of addr a
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Binary file not shown.
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@ -67,6 +67,23 @@
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: (parse*) 0x0a _c RAM+ ;
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: HERE 0x04 _c RAM+ ;
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: CURRENT 0x02 _c RAM+ ;
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: (mmap*) 0x51 _c RAM+ ;
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( The goal here is to be as fast as possible *when there is
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no mmap*, which is the most frequent situation. That is why
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we don't DUP and we rather refetch. That is also why we
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use direct literal instead of RAM+ or (mmap*). )
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: (mmap)
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[ RAMSTART 0x51 + LITN ] _c _@
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IF
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[ RAMSTART 0x51 + LITN ] _c _@ EXECUTE
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THEN
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;
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: @ _c (mmap) _c _@ ;
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: C@ _c (mmap) _c _C@ ;
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: ! _c (mmap) _c _! ;
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: C! _c (mmap) _c _C! ;
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: QUIT
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0 _c FLAGS _c ! _c (resRS)
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@ -204,6 +221,7 @@
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;
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: BOOT
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0 0x51 _c RAM+ _c _!
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LIT< (parse) _c (find) _c DROP _c (parse*) _c !
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( 60 == SYSTEM SCRATCHPAD )
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_c CURRENT _c @ 0x60 _c RAM+ _c !
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@ -233,7 +251,7 @@
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( We cannot use LITN as IMMEDIATE because of bootstrapping
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issues. Same thing for ",".
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32 == NUMBER 14 == compiledWord )
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[ 32 H@ ! 2 ALLOT 14 H@ ! 2 ALLOT ] _c ,
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[ 32 H@ _! 2 ALLOT 14 H@ _! 2 ALLOT ] _c ,
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BEGIN
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_c WORD
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_c (find)
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@ -250,10 +268,10 @@
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;
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( Give ":" and ";" their real name and make them IMMEDIATE )
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0x81 ' X 1 - C!
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':' ' X 4 - C!
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0x81 ' Y 1 - C!
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';' ' Y 4 - C!
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0x81 ' X 1 - _C!
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':' ' X 4 - _C!
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0x81 ' Y 1 - _C!
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';' ' Y 4 - _C!
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( Add dummy entry. we use CREATE because (entry) is, at this
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point, broken. Adjust H@ durint port 2 ping. )
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@ -232,7 +232,7 @@ L2 FSET ( skip )
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BC PUSHqq,
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;CODE
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CODE !
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CODE _!
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HL POPqq,
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DE POPqq,
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chkPS,
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@ -241,7 +241,7 @@ CODE !
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(HL) D LDrr,
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;CODE
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CODE @
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CODE _@
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HL POPqq,
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chkPS,
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E (HL) LDrr,
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@ -250,14 +250,14 @@ CODE @
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DE PUSHqq,
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;CODE
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CODE C!
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CODE _C!
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HL POPqq,
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DE POPqq,
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chkPS,
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(HL) E LDrr,
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;CODE
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CODE C@
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CODE _C@
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HL POPqq,
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chkPS,
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L (HL) LDrr,
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32
notes.txt
32
notes.txt
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@ -88,7 +88,8 @@ RAMSTART INITIAL_SP
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+0e WORDBUF
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+2e SYSVNXT
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+4e INTJUMP
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+51 RESERVED
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+51 MMAPPTR
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+53 RESERVED
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+60 SYSTEM SCRATCHPAD
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+80 RAMEND
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@ -116,6 +117,9 @@ those slots...) in boot binaries are made to jump to this address. If you use
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one of those slots for an interrupt, write a jump to the appropriate offset in
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that RAM location.
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MMAPPTR: Address behind (mmap), which is called before every !/C!/@/C@ world
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to give the opportunity to change the address of the call.
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SYSTEM SCRATCHPAD is reserved for temporary system storage or can be reserved
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by low-level drivers. These are the current usages of this space throughout the
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project:
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@ -154,3 +158,29 @@ can't have comments. This leads to peculiar code in this area. If you see weird
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whitespace usage, it's probably because not using those whitespace would result
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in dict entry creation overwriting the code before it has the chance to be
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interpreted.
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*** Memory maps
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We have a mechanism to map memory ranges to something else. We call this memory
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maps. There is a reserved address in memory for a memory mapping routine. The
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word (mmap*) returns that address. By default, it's zero which means no mapping.
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Each call to @, C@, ! or C! call that word, if nonzero, before executing. This
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allows you to do pretty much anything. Try to be efficient in your programming,
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however, because those words are called *very* often.
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Here's a toy example of memory map usage:
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> 8 0x8000 DUMP
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:00 0000 0000 0000 0000 ........
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> : foo DUP 0x8000 = IF 2 + THEN ;
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> ' foo (mmap*) !
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> 8 0x8000 DUMP
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:00 0000 0000 0000 0000 ........
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> 0x1234 0x8000 !
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> 8 0x8000 DUMP
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:00 3412 3412 0000 0000 4.4.....
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> 0 (mmap*) !
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> 8 0x8000 DUMP
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:00 0000 3412 0000 0000 ..4.....
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>
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