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@ -160,49 +160,11 @@ Then, there's the *special stuff*. This is the list of things you can query for:
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* `$`: the scratchpad.
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**usr**: This calls the memory address specified as an expression argument.
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Before doing so, it sets the registers according to a specific logic: Variable
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`A`'s LSB goes in register `A`, variable `D` goes in register `DE`, `H` in `HL`
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`B` in `BC` and `X` in `IX`. `IY` can't be used because it's used for the jump.
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Then, after the call, the value of the registers are put back into the
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variables following the same logic.
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Let's say, for example, that you want to use the kernel's `printstr` to print
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the contents of the scratchpad. First, you would call `addr $` to put the
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address of the scratchpad in `A`, then do `h=a` to have that address in `HL`
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and, if printstr is, for example, the 21st entry in your jump table, you'd do
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`usr 21*3` and see the scratchpad printed!
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## Optional modules
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As explained in "glueing" section abolve, this folder contains optional modules.
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Here's the documentation for them.
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### blk
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Block devices commands. Block devices are configured during kernel
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initialization and are referred to by numbers.
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**bsel**: Select the active block device. The active block device is the target
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of all commands below. You select it by specifying its number. For example,
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`bsel 0` selects the first configured device. `bsel 1` selects the second.
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A freshly selected blkdev begins with its "pointer" at 0.
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**seek**: Moves the blkdev "pointer" to the specified offset. The first
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argument is the offset's least significant half (blkdev supports 32-bit
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addressing). Is is interpreted as an unsigned integer.
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The second argument is optional and is the most significant half of the address.
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It defaults to 0.
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**getb**: Read a byte in active blkdev at current pointer, then advance the
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pointer by one. Read byte goes in `A`.
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**putb**: Writes a byte in active blkdev at current pointer, then advance the
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pointer by one. The value of the byte is determined by the expression supplied
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as an argument. Example: `putb 42`.
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### fs
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`fs.asm` provides those commands:
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@ -1,47 +0,0 @@
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basBSEL:
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call rdExpr
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ret nz
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push ix \ pop hl
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call blkSelPtr
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ld a, l
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jp blkSel
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basBSEEK:
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call rdExpr
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ret nz
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push ix ; --> lvl 1
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call rdExpr
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push ix \ pop de
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pop hl ; <-- lvl 1
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jr z, .skip
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; DE not supplied, set to zero
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ld de, 0
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.skip:
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xor a ; absolute mode
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call blkSeek
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cp a ; ensure Z
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ret
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basGETB:
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call blkGetB
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ret nz
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ld (VAR_TBL), a
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ret
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basPUTB:
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call rdExpr
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ret nz
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push ix \ pop hl
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ld a, l
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jp blkPutB
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basBLKCmds:
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.dw basBSEL
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.db "bsel", 0, 0
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.dw basBSEEK
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.db "bseek", 0
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.dw basGETB
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.db "getb", 0, 0
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.dw basPUTB
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.db "putb", 0, 0
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.db 0xff, 0xff, 0xff ; end of table
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@ -399,31 +399,6 @@ basADDR:
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.dw SCRATCHPAD
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.db 0
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basUSR:
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call rdExpr
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ret nz
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push ix \ pop iy
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; We have our address to call. Now, let's set up our registers.
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; HL comes from variable H. H's index is 7*2.
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ld hl, (VAR_TBL+14)
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; DE comes from variable D. D's index is 3*2
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ld de, (VAR_TBL+6)
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; BC comes from variable B. B's index is 1*2
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ld bc, (VAR_TBL+2)
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; IX comes from variable X. X's index is 23*2
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ld ix, (VAR_TBL+46)
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; and finally, A
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ld a, (VAR_TBL)
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call callIY
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; Same dance, opposite way
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ld (VAR_TBL), a
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ld (VAR_TBL+46), ix
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ld (VAR_TBL+2), bc
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ld (VAR_TBL+6), de
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ld (VAR_TBL+14), hl
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cp a ; USR never errors out
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ret
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; direct only
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basCmds1:
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.dw basBYE
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@ -460,6 +435,4 @@ basCmds2:
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.db "sleep", 0
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.dw basADDR
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.db "addr", 0, 0
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.dw basUSR
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.db "usr", 0, 0, 0
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.db 0xff, 0xff, 0xff ; end of table
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@ -86,7 +86,6 @@
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.inc "basic/buf.asm"
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.equ BFS_RAMSTART BUF_RAMEND
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.inc "basic/fs.asm"
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.inc "basic/blk.asm"
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.equ BAS_RAMSTART BFS_RAMEND
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.inc "basic/main.asm"
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@ -106,9 +105,6 @@ init:
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basFindCmdExtra:
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ld hl, basFSCmds
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call basFindCmd
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ret z
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ld hl, basBLKCmds
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jp basFindCmd
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emulGetC:
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