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Add adev unit
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@ -30,10 +30,10 @@ to been consistent in their use. Here's their definitions:
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@ - Fetch
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$ - Initialize
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^ - Arguments in their opposite order
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> - Pointer in a buffer
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< - Input
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> - 1. Pointer in a buffer 2. Opposite of "<".
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( - Lower boundary
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) - Upper boundary
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< - Input
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* - Word indirection (pointer to word)
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~ - Container for native code. Usually not an executable word.
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? - Is it ...? (example: IMMED?)
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@ -122,6 +122,16 @@ HERE -- a Push HERE's address
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H@ -- a HERE @
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MOVE a1 a2 u -- Copy u bytes from a1 to a2, starting with a1, going
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up.
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*** Addressed devices ***
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See usage.txt for details.
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ADEV$ -- Initialize adev subsystem
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A@ a -- c Indirect C@
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A! c a -- Indirect C!
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A@* -- a Address for A@ word
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A!* -- a Address for A! word
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AMOVE src dst u -- Same as MOVE, but with A@ and A!
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*** Arithmetic / Bits ***
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34
forth/adev.fs
Normal file
34
forth/adev.fs
Normal file
@ -0,0 +1,34 @@
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( Addressed devices.
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Abstractions to read and write to devices that allow addressed
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access. At all times, we have one active "fetch" device and
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one active "store" device, A@ and A!.
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Those words have the same signature as C@ and C!, and in fact,
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initially default to proxy of those words.
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)
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: ADEVMEM+ 0x55 RAM+ @ + ;
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: A@* 0 ADEVMEM+ ;
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: A!* 2 ADEVMEM+ ;
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: ADEV$
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H@ 0x55 RAM+ !
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4 ALLOT
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['] C@ A@* !
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['] C! A!* !
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;
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: A@ A@* @ EXECUTE ;
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: A! A!* @ EXECUTE ;
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( Same as MOVE, but with A@ and A! )
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( src dst u -- )
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: AMOVE
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( u ) 0 DO
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SWAP DUP I + A@ ( dst src x )
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ROT SWAP OVER I + ( src dst x dst )
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A! ( src dst )
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LOOP
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2DROP
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;
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@ -90,7 +90,8 @@ RAMSTART INITIAL_SP
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+4e INTJUMP
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+51 CURRENTPTR
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+53 readln's variables
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+55 FUTURE USES
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+55 adev's variables
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+57 FUTURE USES
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+59 z80a's variables
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+5b FUTURE USES
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+70 DRIVERS
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36
usage.txt
36
usage.txt
@ -86,3 +86,39 @@ flag to true. For example, "<>{ <>}" yields true.
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To check whether A is in between B and C inclusively, you would write:
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A <>{ B 1 - &> C 1 + &< <>}
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*** Addressed devices
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The adev unit provides a simple but powerful abstraction over C@ and C!: A@ and
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A!. These work the same way as C@ and C! (but for performance reasons, aren't
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used in core words), but are indirect calls.
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Upon initialization, the default to C@ and C!, but can be set to any word
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through A@* and A!*.
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On top of that, it provides a few core-like words such as AMOVE.
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Let's demonstrate its use through a toy example:
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> : F! SWAP 1 + SWAP C! ;
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> 8 H@ DUMP
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:54 0000 0000 0000 0000 ........
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> 9 H@ A!
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> 8 H@ DUMP
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:54 0900 0000 0000 0000 ........
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> ' F! A!* !
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> 9 H@ 1 + A!
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> 8 H@ DUMP
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:54 090a 0000 0000 0000 ........
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> H@ H@ 2 + 2 AMOVE
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> 8 H@ DUMP
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:54 090a 0a0b 0000 0000 ........
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>
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Of course, you might want to end up using adev in this kind of ad-hoc way to
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have some kind of mapping function, but what you'll mostly want to to is to
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plug device drivers into those words.
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