Fifth - virtual machine
+Table of Contents
+ ++Current emulator emulates: +
+-
+
- 1 CPU. +
- It has 2 stacks +
- ~50 instructions +
- 4GB flat address space (theoretically). +
+While I tried to keep instruction set simple, I was forced to put in +some complex instructions to make performance acceptable on +emulator. +
+ ++CPU has following registers: +
+-
+
- IP
- instruction pointer +
- DSP
- data stack pointer +
- RSP
- return stack pointer +
1. Instructions overview
++Virtual CPU, commands (most of them are avaiable as ordinary commands +in programming language): +
+ + +| # | +name | +stack footprint | +description | +
|---|---|---|---|
| 0 | +nop | +-- | +does nothing | +
| 1 | +halt | +-- | +halt CPU ( return to DOS on emulator ) | +
| 2 | +kbd@ | +– c | +read scancode of pressed or released key | +
| 3 | +num <dword> | +– n | +put immidiate number into datastack | +
| 4 | +jmp <dword> | +-- | +jump to specified code | +
| 5 | +call <dword> | ++ | jump to specified code, save return address to return stack | +
| 6 | +1+ | +n – n+1 | ++ |
| 7 | +1- | +n – n-1 | ++ |
| 8 | +dup | +n – n n | +duplicate top of data stack | +
| 9 | +drop | +n -- | +drop last element in data stack | +
| 10 | +if <dword> | +n -- | +jump to addr if top element was 0 | +
| 11 | +ret | ++ | jump to code, specified in return stack. | +
| 12 | +c@ | +addr – n | +read byte from memory at specified address | +
| 13 | +c! | +n addr -- | +store byte to specified memory | +
| 14 | +push | +DSTK -> RSTK | +move top of datastack to returnstack | +
| 15 | +pop | +RSTK -> DSTK | +move top of returnstack to datastack | +
| 16 | +<unused> | ++ | + |
| 17 | +rot | +n1 n2 n3 – n2 n3 n1 | +rotate stack elements | +
| 18 | +disk@ | +FromDiskSect ToMem -- | +read 1KB from disk into RAM | +
| 19 | +disk! | +FromMem ToDiskSect -- | +write 1KB to disk | +
| 20 | +@ | +addr – n | +read 32 bit number from memory | +
| 21 | +! | +n addr -- | +store 32 bit number to memory | +
| 22 | +over | +n1 n2 – n1 n2 n1 | ++ |
| 23 | +swap | +n1 n2 – n2 n1 | ++ |
| 24 | ++ | +n1 n2 – n1+n2 | ++ |
| 25 | +- | +n1 n2 – n1-n2 | ++ |
| 26 | +* | +n1 n2 – n1*n2 | ++ |
| 27 | +/ | +n1 n2 – n1/n2 | ++ |
| 28 | +> | +n1 n2 – result | +is true when n1 > n2 | +
| 29 | +< | +n1 n2 – result | +is true when n1 < n2 | +
| 30 | +not | +n1 – not_n1 | +logical not | +
| 31 | +i | +– n | +copies top of return stack into datastack | +
| 32 | +cprt@ | +addr – n | +read one byte from hardware port | +
| 33 | +cprt! | +n addr -- | +store one byte to hardware port | +
| 34 | +i2 | +– n | +like "i" but takes second top stack element | +
| 35 | +i3 | +– n | +like "i" but takes third top stack element. | +
| 36 | +shl | +n amount – n | +left bit shift | +
| 37 | +shr | +n amount – n | +right bit shift | +
| 38 | +or | +n1 n2 – n | +logical or | +
| 39 | +xor | +n1 n2 – n | +exclusive logical or | +
| 40 | +vidmap | +addr -- | +copy memory from "addr" to video memory. | +
| 41 | +mouse@ | +– x y button | +read mouse coordinates & buttons | +
| 42 | +vidput | +addr1 addr2 x y -- | +put image1 into image2, at location x, y | +
| 43 | +cmove | +addr1 addr2 amount | +move memory from addr1 to addr2 | +
| 44 | +cfill | +c addr amount -- | +fill memory starting at "addr" with "c" bytes. | +
| 45 | +tvidput | +addr1 addr2 x y -- | +put image with transparency support | +
| 46 | +depth | +– depth | +returns current depth of data stack. | +
| 47 | +charput | +colorfg colorbg addrsrc addrdest x y | +draw text character | +
1.1. kbd@ - read scancode of pressed or released key
++Returns 0 if no data available. +
+1.2. vidput - put image1 into image2, at location x, y
++Does clipping, so part of a big image can be mapped into smaller one. +
+1.3. cmove - copy memory array
++Move memory from addr1 to addr2. If addr1 is greater than addr2 then +count address foward while moving, elseway starts from end and counts +backwards, so no data loss occurs when memory regions partially +overlap. +
+1.4. tvidput - put image with transparency support
++Stack footprint +
++addr1 addr2 x y -- ++ + +
+Put image1 into image2, at location x, y with transparency support +
+ ++Color 255 in source image is treated as transparent. +
+1.5. charput - draw text character
++Draw character to image buffer located at "addrdest" to specified x & +y location. Decodes 8 bytes from source to bits, used to draw +character. +
+