Editing Wikifang:Network Translation Patchsite/BugVM

Bugsite contains a virtual machine which executes all (non-IRQ) game logic. It is a stack-based virtual machine with a large number of opcodes specific to the game.

== Data and Link Stacks ==
Two stacks are managed by the VM: a link stack and a data stack. The link stack ('''$C100''') supports up to $3F call frames of 4 bytes each, which is manipulated entirely by the call, jump-far, and return opcodes. The data stack ('''$C200''') supports up to $55 data items of 3 bytes each. Each data item consists of a little-endian 16-bit word followed by a tag byte, which specifies if it's...

* '''$3D''' an immediate value
* '''$1D''' a word index into the indirect memory array
* '''$1E''' a bit index into the predicate array

Data items are pushed onto the stack as immediate values and then cast to indirect or predicate offsets as necessary. Both stacks grow upwards from their base address.

=== Indirect & Predicate Memory ===
BugVM allows direct access (read and write) to indirect and predicate memory. Indirect memory covers WRAM3:$C400 to WRAM3:$D7FF, and is indexed using word offsets. Predicate memory covers WRAM3:$D800 to WRAM3:$DFFF and is indexed as a massive bitfield.

Indirect and predicate memory can be saved to and loaded from SRAM using opcodes $47 and $48, along with additional data in SRAM.

=== Known Indirect Memory Slots ===

{| class="wikitable"
|-
! Index !! WRAM Addr. !! Name !! Purpose
|-
| $01 || $C402 || W_System_GameVersion || Stores the version of the game the user is playing.

0 is Alpha version, 1 is Beta version
|-
| $12 || $C424 || W_BugVM_StringArena || Stores the current location of the end of the string-builder arena, used by the DB opcode to store embedded string data.
|-
| $172 || $C6E4 || W_MainScript_PortraitID || Stores the currently selected character portrait, if any.
|-
| $580 - $59F || $CF00-$CF3F || W_Battle_AttrStaging || Stores the most recently loaded RPG Attribute Table entry.
|}

== Linkage Directory (BugFS) ==
Bugsite contains a filesystem which almost pervasively enumerates all resources within the game. Each file is exclusively referred to with it's 16-bit linkage identifier; there are no file names and only one directory. Almost all resource loads, except some game data tables, are mediated through BugFS. Graphics and tilemaps are loaded by ID and BugVM code can farjump/farcall to the start of another section by ID.

The directory's structure is that of an array of entry structures. The directory array starts at $A:$4000, and the ID indexes this array by 8 bytes. Directory entries appear to be stored in the same order as where their data is stored in ROM. The directory spans $1000 entries, across 2 banks; though it could be extended further if the referenced data were to be moved to a later bank. Approximately 40 entries at the end of the directory are zero-size files (pointing to ROM $7F:70FF) and may be unused filler entries.

{| class="wikitable"
|-
! Offset !! Name !! Type !! 
|-
| $0 || Bank || 8-bit bank index ||
|-
| $1 || Offset || 16-bit offset || Offset is relative to $4000, not a pointer
|-
| $3 || Size || 16-bit size ||
|}

Each directory entry is 5 bytes long. Fields include a bank index, byte offset into that bank (0 means a pointer of $4000), and total size. Much like the directory itself, files are allowed and expected to span across bank boundaries. Native code that reads BugFS files will need to account for bank switching. Directory entries are stored with an 8-byte alignment (3 padding bytes).

== RPG Attribute Tables ==

Certain tables of game attributes are not stored as BugFS files. These data tables include listings for monsters, battle moves, chips, key items, and encounters. Not much is known about these tables, except for the fact that they are universally arrays of $40 bytes and often contain a name string at offset $30. Specialized BugVM instructions exist to load a single table entry into W_Battle_AttrStaging and to print the name at offset $30.

{| class="wikitable"
|-
! Location !! Size !! Contents !! 
|-
| $4:4000, $5:4000 || $4000 || Bugs || Instructions that read from the monster table will select bank $4 for Alpha Version and bank $5 for Beta Version. Beta's table is present and unmodified in Alpha, and vice versa.
|-
| $6:4000 || $4000 || Moves || 
|-
| $7:4000 || $A80 || Chips || After the entry at $7:4A40 none of the remaining items in this table appear to have valid name data and are thus likely to be something else.
|-
| $7:6000 || $1240 || Key Items || After the entry at $7:7200 none of the remaining items in this table appear to have valid name data and are thus likely to be something else.
|-
| $8:4000, $9:4000 || $4000 || Encounters || Instructions that read from the encounter table will select bank $8 for Alpha Version and bank $9 for Beta Version. Beta's table is present and unmodified in Alpha, and vice versa.
|}

== Initial State ==
Execution of BugVM always starts from the beginning of linkage $0. Indirect and predicate memory is set to $0 upon game initialization.

== Instruction Set ==
BugVM takes instructions as 8-bit opcodes which can optionally accept additional parameters. Most opcodes take arguments from the stack, rather than from the instruction stream. Native implementations for a particular opcode are referenced from the opcode table at $3E00, reproduced below:

{| class="wikitable"
|-
! !! x0 !! x1 !! x2 !! x3 !! x4 !! x5 !! x6 !! x7 !! x8 !! x9 !! xA !! xB !! xC !! xD !! xE !! xF
|-
! 0x
| NOP <br> [[#op_5E9|$5E9]] || ENOP $01 <br> [[#op_5E9|$5E9]] || ENOP $02 <br> [[#op_5E9|$5E9]] || ARFREE <br> [[#op_671|$671]] || ENOP $04 <br> [[#op_5E9|$5E9]] || ENOP $05 <br> [[#op_5E9|$5E9]] || STR <br> [[#op_68C|$68C]] || SUML <br> [[#op_6C0|$6C0]] || ANDL <br> [[#op_6CA|$6CA]] || OR <br> [[#op_6D7|$6D7]] || XOR <br> [[#op_6E2|$6E2]] || AND <br> [[#op_6ED|$6ED]] || CMP_EQ <br> [[#op_6F8|$6F8]] || CMP_NEQ <br> [[#op_705|$705]] || CMP_LT <br> [[#op_712|$712]] || CMP_LEQ <br> [[#op_723|$723]]
|-
! 1x
| CMP_GT <br> [[#op_752|$752]] || CMP_GEQ <br> [[#op_763|$763]] || ??? <br> $772 || SLA <br> [[#op_784|$784]] || SUB <br> [[#op_796|$796]] || ADD <br> [[#op_7A1|$7A1]] || MOD <br> [[#op_7A9|$7A9]] || DIV <br> [[#op_7C3|$7C3]] || MUL <br> [[#op_7ED|$7ED]] || PNOP $19 <br> [[#op_80B|$80B]] || PNOP $1A <br> [[#op_80C|$80C]] || PNOP $1B <br> [[#op_80D|$80D]] || PNOP $1C <br> [[#op_80E|$80E]] || INDIR <br> [[#op_80F|$80F]] || PRED <br> [[#op_820|$820]] || ENOP $1F <br> [[#op_5E9|$5E9]]
|-
! 2x
| ENOP $20 <br> [[#op_5E9|$5E9]] || ENOP $21 <br> [[#op_5E9|$5E9]] || ENOP $22 <br> [[#op_5E9|$5E9]] || ENOP $23 <br> [[#op_5E9|$5E9]] || ENOP $24 <br> [[#op_5E9|$5E9]] || ENOP $25 <br> [[#op_5E9|$5E9]] || ENOP $26 <br> [[#op_5E9|$5E9]] || ENOP $27 <br> [[#op_5E9|$5E9]] || ENOP $28 <br> [[#op_5E9|$5E9]] || ENOP $29 <br> [[#op_5E9|$5E9]] || ENOP $2A <br> [[#op_5E9|$5E9]] || ENOP $2B <br> [[#op_5E9|$5E9]] || POPALL <br> [[#op_831|$831]] || ENOP $2D <br> [[#op_5E9|$5E9]] || ENOP $2E <br> [[#op_5E9|$5E9]] || PNOP $2F <br> [[#op_835|$835]]
|-
! 3x
| PNOP $30 <br> [[#op_836|$836]] || PNOP $31 <br> [[#op_837|$837]] || PNOP $32 <br> [[#op_838|$838]] || PNOP $33 <br> [[#op_839|$839]] || PNOP $34 <br> [[#op_83A|$83A]] || PNOP $35 <br> [[#op_87B|$87B]] || NPREF <br> [[#op_87C|$87C]] || JMPT <br> [[#op_887|$887]] || JMP <br> [[#op_8AC|$8AC]] || RET <br> [[#op_8BB|$8BB]] || PNOP $3A <br> [[#op_8DB|$8DB]] || PNOP $3B <br> [[#op_8DC|$8DC]] || PNOP $3C <br> [[#op_8DD|$8DD]] || IMMED <br> [[#op_8DE|$8DE]] || DB <br> [[#op_941|$941]] || JAL <br> [[#op_8F0|$8F0]]
|-
! 4x
| WINWAIT <br> [[#op_A12|$A12]] || || || || || || || || || || || || PRINT <br> [[#op_A84|$A84]] || || ||
|-
! 5x
| SCRCURS <br> [[#op_C54|$C54]] || || || || || || || || || || WINDIALOG <br> [[#op_AED|$AED]] || WINCLR <br> [[#op_97C|$97C]] || || || || RESLD <br> [[#op_9C6|$9C6]]
|-
! 6x
| || SPRINPUT <br> [[#op_A29|$A29]] || || || || || || || || || FARCALL <br> [[#op_91B|$91B]] || FARJMP <br> [[#op_83B|$83B]] || || || SPRANIM <br> [[#op_2775|$2775]] || SPRPOSPLAY <br> [[#op_2788|$2788]]
|-
! 7x
| WINCHOICE <br> [[#op_13B4|$13B4]] || || TILELD <br> [[#op_1BAC|$1BAC]] || || || PALLD <br> [[#op_2F0E|$2F0E]] || || || SPRCHOREO <br> [[#op_3269|$3269]] || || || || || WINCOORD <br> [[#op_C24|$C24]] || WINCURS <br> [[#op_C63|$C63]] ||
|-
! 8x
| || || WINBRK <br> [[#op_ADA|$ADA]] || || || || TMAPSAV <br> [[#op_1C92|$1C92]] || || || || || || SPRDIR <br> [[#op_324F|$324F]] || || SPRWIPE <br> [[#op_289C|$289C]] ||
|-
! 9x
| || || SPRPLAY <br> [[#op_27B3|$27B3]] || || || || || || || || || || || || || PRKEY <br> [[#op_165A|$165A]]
|-
! Ax
| BLKKEY <br> [[#op_42A|$42A]] || PRMOVE <br> [[#op_1668|$1668]] || BLKMOVE <br> [[#op_3FE|$3FE]] || || || PRNAME <br> [[#op_162A|$162A]] || SPRCTRL <br> [[#op_235E|$235E]] || SPRFINISH <br> [[#op_2386|$2386]] || || || || || || WINFRARROW <br> [[#op_B05|$B05]] || || PRMON <br> [[#op_1622|$1622]]
|-
! Bx
| NTSTR <br> [[#op_1677|$1677]] || NTPRINT <br> [[#op_1670|$1670]] || WINOPEN <br> [[#op_B2D|$B2D]] || WINFRAME <br> [[#op_AFC|$AFC]] || || || || || || || || BLKMON <br> [[#op_39C|$39C]] || || || ||
|-
! Cx
| || || || || || || SPRWAIT <br> [[#op_27BB|$27BB]] || || || || || SPRFREEZE <br> [[#op_32C7|$32C7]] || SPRTHAW <br> [[#op_32D5|$32D5]] || || || SPRHIDE <br> [[#op_2877|$2877]]
|-
! Dx
| || || SPRHOLD <br> [[#op_A39|$A39]] || || || || || || || WININPUT <br> [[#op_A1D|$A1D]] || || || || || ||
|-
! Ex
| || || BLKCHIP <br> [[#op_456|$456]] || PRCHIP <br> [[#op_1661|$1661]] || || PRNICK <br> [[#op_1638|$1638]] || || || || || || || || || ||
|-
! Fx
| || BLKENC <br> [[#op_3CD|$3CD]] || || || WINARROW <br> [[#op_B10|$B10]] || || || || || || || || || || ||
|}

=== Boolean Logic & Comparison Operators ===
As convention for this table we treat zero as boolean TRUE and one as boolean FALSE. Other non-zero values are treated as FALSE, but boolean opcodes will not return nonstandard values.

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_6C0'
| SUML <br> (SUM Logical) || $07 || $6C0 || None || arg1, arg2 (TOP) -> bool (TOP) || Add arg1 and arg2. Push TRUE if result is zero, FALSE if non-zero.
|- id='op_6CA'
| ANDL <br> (AND Logical) || $08 || $6CA || None || arg1, arg2 (TOP) -> bool (TOP) || Bitwise-AND arg1 and arg2. Push TRUE if result is zero, FALSE if non-zero.
|- id='op_6F8'
| CMP_EQ <br> (CoMParison EQual) || $0C || $6F8 || None || arg1, arg2 (TOP) -> bool (TOP) || Compare arg1 and arg2. Push TRUE if both arguments are equal, FALSE otherwise.
|- id='op_705'
| CMP_NEQ <br> (CoMParison Not EQual) || $0D || $705 || None || arg1, arg2 (TOP) -> bool (TOP) || Compare arg1 and arg2. Push TRUE if both arguments are not equal, FALSE otherwise.
|- id='op_712'
| CMP_LT <br> (CoMParison Less Than) || $0E || $712 || None || arg1, arg2 (TOP) -> bool (TOP) || Compare arg1 and arg2. Push TRUE if arg1 is less than arg2, FALSE otherwise.
|- id='op_723'
| CMP_LEQ <br> (CoMParison Less or EQual) || $0F || $723 || None || arg1, arg2 (TOP) -> bool (TOP) || Compare arg1 and arg2. Push TRUE if arg1 is less than or equal to arg2, FALSE otherwise.
|- id='op_752'
| CMP_GT <br> (CoMParison Greater Than) || $10 || $752 || None || arg1, arg2 (TOP) -> bool (TOP) || Compare arg1 and arg2. Push TRUE if arg1 is greater than arg2, FALSE otherwise.
|- id='op_763'
| CMP_GEQ <br> (CoMParison Greater or EQual) || $11 || $763 || None || arg1, arg2 (TOP) -> bool (TOP) || Compare arg1 and arg2. Push TRUE if arg1 is greater than or equal to arg2, FALSE otherwise.
|}

=== Bitwise logic ===

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_6D7'
| OR <br> (bitwise OR) || $09 || $6D7 || None || arg1, arg2 (TOP) -> value (TOP) || Bitwise-OR arg1 and arg2 as the return value.
|- id='op_6E2'
| XOR <br> (bitwise eXclusive OR) || $0A || $6E2 || None || arg1, arg2 (TOP) -> value (TOP) || Bitwise-XOR arg1 and arg2 as the return value.
|- id='op_6ED'
| AND <br> (bitwise AND) || $0B || $6ED || None || arg1, arg2 (TOP) -> value (TOP) || Bitwise-AND arg1 and arg2 as the return value.
|- id='op_784'
| SLA <br> (Shift-Left Arithmetic) || $13 || $784 || None || bits, shift (TOP) -> value (TOP) || Shift '''bits''' left, '''shift''' times, while inserting zero bits, to produce '''value'''.
|}

=== Arithmetic ===

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_796'
| SUB <br> (SUBtraction) || $14 || $796 || None || minuend, subtrahend (TOP) -> difference (TOP) || Subtract '''subtrahend''' from '''minuend''' to produce '''difference'''.
|- id='op_7A1'
| ADD <br> (ADDition) || $15 || $7A1 || None || addend1, addend2 (TOP) -> sum (TOP) || Add '''addend1''' to '''addend2''' to produce '''sum'''.
|- id='op_7A9'
| MOD <br> (MODulo) || $16 || $7A9 || None || dividend, divisor (TOP) -> remainder (TOP) || Integer-divide '''dividend''' by '''divisor''' and return only the '''remainder'''.
|- id='op_7C3'
| DIV <br> (DIVide) || $17 || $7C3 || None || dividend, divisor (TOP) -> quotient (TOP) || Integer-divide '''dividend''' by '''divisor''' and return only the '''quotient'''.
|- id='op_7ED'
| MUL <br> (MULtiply) || $18 || $7ED || None || multiplicand, multiplier (TOP) -> product (TOP) || Multiply '''multiplicand''' by '''multiplier''' to produce the '''product'''.
|}

=== Memory & Stack Manipulation ===

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_68C'
| STR <br> (SToRe) || $06 || $68C || None || &address, value (TOP) -> (TOP) || Store the value at the memory location referenced by &address. The exact memory operations performed depend on the target of *address.

If address is an indirect index, the memory location referenced by *address will be set to value.

If address is a predicate index, the bit referenced by *address will be set or reset based on if value is zero or non-zero.

It is illegal to STR into an immediate value, and doing so will cause the VM to halt operation.
|- id='op_80F'
| INDIR <br> (INDIRect) || $1D || $80F || None || immed (TOP) -> &address (TOP) || Cast the value '''immed''' into an indirect memory index &'''address'''.
|- id='op_820'
| PRED <br> (PREDicate) || $1E || $820 || None || immed (TOP) -> &pred (TOP) || Cast the value '''immed''' into a predicate memory index &'''pred'''.
|- id='op_831'
| POPALL <br> (POP ALL) || $2C || $831 || None || (...) -> (EMPTY) || Empty the stack.
|- id='op_8DE'
| IMMED <br> (IMMEDiate) || $3D || $8DE || immed (16b) || (TOP) -> immed (TOP) || Push '''immed''' onto the data stack as an immediate value.
|- id='op_941'
| DB <br> (Declare Bytes) || $3E || $941 || string (null-terminated) || (TOP) -> straddr (TOP) || Copy null-terminated string data from the instruction stream into the string-building arena referred to by '''$C424'''.

The address of the newly copied string data will be pushed onto the data stack as an immediate value.
|- id='op_671'
| ARFREE <br> (ARena FREE) || $03 || $671 || None || None || Free the data in the string arena (or set up the string arena if it hasn't already been done).

This opcode should be used as soon as possible after you are done with the data in the string arena. The arena has a maximum capacity of 255 bytes, and memory is not reclaimed from use by a [[#op_941|DB]] opcode until you ARFREE the entire arena.
|- id='op_1677'
| NTSTR <br> (Name Temporary SToRe) || $B0 || $1677 || None || srcaddr (TOP) -> (TOP) || Store string data in the naming temporary string area.

This is primarily used by naming / password screens which need to redraw themselves while retaining the user's input data. srcaddr is the address of a string, usually provided by the DB opcode.

The naming temporary area has a maximum size of $E bytes, not counting the mandatory null terminator.
|}

=== Execution Control ===
Execution Control opcodes control the address of the next instruction to execute, determined by BugVM's program counter. It consists of a '''bank address''', '''base address''', and '''offset address'''. The linkage directory determines what the bank and base addresses of a section are. The offset address is added to the base in order to calculate the address of the next instruction.

Caution: Parameters named "offset" for jump instructions refer to the program counter offset address, and do not imply the existence of PC-relative jumps instructions within Bugsite.

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_887'
| JMPT <br> (JuMP if True) || $37 || $887 || offset (16b) || bool (TOP) -> (TOP) || Jump to a new offset within the current linkage section if '''bool''' is TRUE.
|- id='op_8AC'
| JMP <br> (JuMP) || $38 || $8AC || offset (16b) || None || Jump to a new offset within the current linkage section.
|- id='op_8BB'
| RET <br> (RETurn) || $39 || $8BB || None || None || Return to the previously linked return address.
|- id='op_8F0'
| JAL <br> (Jump And Link) || $3F || $8F0 || offset (16b) || None || Jump to a new offset within the current linkage section. Store the offset of the next instruction on the link stack.
|- id='op_91B'
| FARCALL || $6A || $91B || None || linkage_index (TOP) -> (TOP) || Jump to the start of a new linkage section. Store the offset of the next instruction on the stack.
|- id='op_83B'
| FARJMP <br> (FAR JuMP) || $6B || $83B || None || linkage_index (TOP) -> (TOP) || Jump to the start of a new linkage section, erasing the link stack in the process.

The previous linkage section is stored for later use.
|}

=== NOP and NOP-alikes ===
BugVM contains a number of opcodes which do nothing, including both a single implementation of a NOP opcode used to fill in blank spots in the table as well as individual implementations which presumably did something in the past.

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_5E9'
| NOP <br> (Null OPeration),<br> ENOP $nn (Effective Null OPeration) || Too many to list || $5E9 || None || None || Does nothing.

This particular null-op implementation is used many times to fill space in the opcode table.
|- id='op_80B'
| PNOP $19 <br> (Probable Null OPeration) || $19 || $80B || None || None || Does nothing.
|- id='op_80C'
| PNOP $1A <br> (Probable Null OPeration) || $1A || $80C || None || None || Does nothing.
|- id='op_80D'
| PNOP $1B <br> (Probable Null OPeration) || $1B || $80D || None || None || Does nothing.
|- id='op_80E'
| PNOP $1C <br> (Probable Null OPeration) || $1C || $80E || None || None || Does nothing.
|- id='op_835'
| PNOP $2F <br> (Probable Null OPeration) || $2F || $835 || None || None || Does nothing.
|- id='op_836'
| PNOP $30 <br> (Probable Null OPeration) || $30 || $836 || None || None || Does nothing.
|- id='op_837'
| PNOP $31 <br> (Probable Null OPeration) || $31 || $837 || None || None || Does nothing.
|- id='op_838'
| PNOP $32 <br> (Probable Null OPeration) || $32 || $838 || None || None || Does nothing.
|- id='op_839'
| PNOP $33 <br> (Probable Null OPeration) || $33 || $839 || None || None || Does nothing.
|- id='op_83A'
| PNOP $34 <br> (Probable Null OPeration) || $34 || $83A || None || None || Does nothing.
|- id='op_87B'
| PNOP $35 <br> (Probable Null OPeration) || $35 || $87B || None || None || Does nothing.
|- id='op_87C'
| NPREF <br> (Null PREFix) || $36 || $87C || opcode, ??? || None || Executes the next opcode as normal.

This would appear to be just another NOP, but it's native implementation actually loads and executes the next byte as an opcode. Hence, it works like a prefix byte that does nothing.

Perhaps in a previous revision of the game, NPREF had a use.
|- id='op_8DB'
| PNOP $3A <br> (Probable Null OPeration) || $3A || $8DB || None || None || Does nothing.
|- id='op_8DC'
| PNOP $3B <br> (Probable Null OPeration) || $3B || $8DC || None || None || Does nothing.
|- id='op_8DB'
| PNOP $3C <br> (Probable Null OPeration) || $3C || $8DB || None || None || Does nothing.
|}

=== Graphics Functions ===

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_1BAC'
| TILELD <br> (TILE LoaD) || $72 || $1BAC || None || linkage_index, tile_x, tile_y, base_tile, base_attr (TOP) -> (TOP) || Load a precomposed tilemap from BugFS file linkage_index into the first tilemap in VRAM ($9800).

The base_tile and base_attr parameters allow the user to add a dynamic tile index and palette index offset to the tilemap. For example, if you loaded the tilemap's graphics into slot $30 on the second VRAM tile bank, with color data starting at BG palette 3, you could set base_tile to $30 and base_attr to Bank 1, Palette 3.

Tile X and Y coordinates allow you to control where the tilemap data is written. These coordinates are in tile units and are relative to the first visible tile on the screen (based on the current screen scroll).

Each tilemap's data starts with the width and height of the tilemap, followed by two bytes for each tile's ID and attributes, starting from the top-left of the tilemap and continuing right until the end, then the next line down. These IDs and attributes are relative to the base parameters as described above.
|- id='op_9C6'
| RESLD <br> (RESource LoaD) || $5F || $9C6 || None || linkage_index, copy_start, copy_len, target_addr, target_bank (TOP) -> (TOP) || Load graphics resources from BugFS file linkage_index into tile memory.

copy_start determines how far into the resource to copy from, and copy_len determines how much to copy from that point. Both of these are in units of 32 bytes - exactly the size of a single tile.

target_addr and target_bank determines where to place the copied resources in VRAM. They are native memory pointers, not indexed to anything.
|- id='op_2F0E'
| PALLD <br> (PALette LoaD) || $75 || $2F0E || None || linkage_index, is_bgpal, source_palette, target_palette (TOP) -> (TOP) || Copy a color palette into color palette memory.

Palette color data will be copied from source_palette palettes into the file at linkage_index, into color memory at the given target_palette. If is_bgpal is True then the color data will be loaded into background palette memory; otherwise, color data will load into object palette memory.

source_palette and target_palette are both palette indices; it is not possible to copy part of a palette, or unaligned data from the filesystem.
|- id='op_C63'
| SCRCURS <br> (SCReen CURSor) || $7E || $C63 || None || x, y (TOP) -> (TOP) || Set the tile cursor relative to the screen.

The tile cursor is a screen offset in increments of 8x8 pixels, used to control the positioning of various graphical operations on the screen, such as [[#op_A84|PRINT]]ing text.
|- id='op_A84'
| PRINT <br> (PRINT) || $4C || $A84 || None || string_addr (TOP) -> (TOP) || Print tile text onto the screen.

Printed text will appear on screen at the current tile cursor - usually set by an opcode like [[#op_C54|SCRCURS]], [[#op_C63|WINCURS]], or [[#op_C24|WINCOORD]].

string_addr points to a null-terminated string in unbanked memory - usually some portion of the string arena that is written to by [[#op_941|DB]]. Since that opcode returns an unbanked memory pointer on stack, one can print to the screen using just DB and PRINT opcodes.

The character $7F is special-cased in this function to print the player's name at $C9F0.

PRINT uses tile text in order to draw letters. A tile font must have been previously loaded in VRAM at tile location 0; it's encoded character value will be used as a tile index to draw with.
|- id='op_1670'
| NTPRINT <br> (Name Temporary PRINT) || $B0 || $1677 || None || None || Print stored string data in the naming temporary area.
|- id='op_1C92'
| TMAPSAV <br> (Tile MAP SAVe) || $86 || $1C92 || None || None || Copy the contents of tile map 1 ($9800) to tile map 2 ($9C00).
|}

=== Window Management ===
Windows are regions of the background layer adorned with a border, intended to be drawn over the active playfield to represent dialogue or certain kinds of menus.

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_C24'
| WINCOORD <br> (WINdow COORDinate) || $7D || $C24 || None || xmin, ymin, xmax, ymax (TOP) -> (TOP) || Set the coordinates of the current window.

xmin, ymin, xmax, ymax are the screen pixel coordinates of the left, top, right, and bottom edges of the window, respectively; including the frame. They will be used to configure Window Manager variables for other WINnn opcodes.

The tile cursor will be set to the X and Y coordinates of the ''contents'' of the specified window, so you can [[#op_A84|PRINT]] to it immediately. This is equivalent to [[#op_C63|WINCURS]] with an x and y of zero.
|- id='op_AFC'
| WINFRAME <br> (WINdow FRAME) || $B3 || $AFC || None || None || Draw the current window's frame.

You must have an active window style loaded into VRAM.

If this window is a menu, and the item counts are configured correctly, WINFRAME will also draw the overflow arrows.
|- id='op_B05'
| WINFRARROW <br> (WINdow FRame ARROW) || $AD || $B05 || None || arrow_position (TOP) -> (TOP) || Draw the current window's frame, with overflow arrows.

This is equivalent to [[#op_AFC|WINFRAME]] + [[#op_B10|WINARROW]] all at once.
|- id='op_B2D'
| WINOPEN <br> (WINdow OPEN) || $B2 || $B2D || None || None || Animate the current window opening.

This animation requires that the window span the whole width of the screen and that [[#op_1C92|TMAPSAV]] had been used to copy the screen before the window frame was drawn (e.g. with [[#op_AFC|WINFRAME]]). Execution of BugVM code is halted until the animation completes.
|- id='op_AED'
| WINDIALOG <br> (WINdow DIALOG) || $5A || $AED || None || None || Draw and open the current window.

This is equivalent to [[#op_1C92|TMAPSAV]] + [[#op_AFC|WINFRAME]] + [[#op_B2D|WINOPEN]] all at once.
|- id='op_97C'
| WINCLR <br> (WINdow CLeaR) || $5B || $97C || None || None || Clear the active window region.

Tiles will be set to $20, which is the encoded byte for a space. In any loaded font, this tile is intended to be blank.
|- id='op_C63'
| WINCURS <br> (WINdow CURSor) || $7E || $C63 || None || x, y (TOP) -> (TOP) || Set the tile cursor relative to the window.
|- id='op_13B4'
| WINCHOICE <br> (WINdow CHOICE) || $70 || $13B4 || None || choice, choice, (...) -> (EMPTY) || Print a series of menu choices.

Each choice will be prefixed with a space, to make room for the selection cursor. They will also be printed single-spaced, as opposed to normal line printing which is double-spaced.

The choice arguments are string pointers (e.g. from [[#op_941|DB]]); this opcode consumes all pointers on the data stack.
|- id='op_B10'
| WINARROW <br> (WINdow ARROW) || $F4 || $B10 || None || arrow_position (TOP) -> (TOP) || Draw overflow arrows for a given menu position.

''arrow_position'' is the index of a particular selected menu choice. Overflow arrows will be drawn on top of the window frame based on this value.
|- id='op_A12'
| WINWAIT <br> (WINdow WAIT) || $60 || $A12 || None || None || Wait for user input.

BugVM execution will halt until the user presses the "A" button on the system. A blinking A-button prompt will be displayed at the bottom-right of the window range.
|- id='op_A1D'
| WININPUT <br> (WINdow INPUT) || $D9 || $A1D || None || (TOP) -> input_changed (TOP) || Wait for user input.

BugVM execution will halt until the user presses any button on the system. A blinking A-button prompt will be displayed at the bottom-right of the window range.

The state of which buttons were pressed to continue is returned on the stack. The format for input data is that of eight bit-flags; from highest to lowest: Start, Select, Button B, Button A, Down, Up, Left, and Right. The upper 8 bits of data are always zero.
|- id='op_97C'
| WINBRK <br> (WINdow BReaK) || $82 || $ADA || None || None || Insert a 'page break' of sorts between two full windows' worth of text.

Internally this is equivalent to a WINWAIT followed by a WINCLR.
|}

=== Sprite Management ===
BugVM contains a fully featured metaspriting and animation system, which we've nicknamed Sprite Manager.

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_324F'
| SPRDIR <br> (SPRite DIRection) || $8C || $324F || None || slot, direction (TOP) -> (TOP) || Set the facing direction of a given sprite.

''slot'' refers to the sprite to control (0 thru 7) and ''direction'' is the direction to make it face. If either are invalid, then nothing will happen. Consult [[Wikifang:Network Translation Patchsite/SpriteManager#Metasprite_Data_Structure|SpriteManager documentation]] for more information on which direction numbers are valid.
|- id='op_235E'
| SPRCTRL <br> (SPRite ConTRoL) || $A6 || $235E || None || slot, input (TOP) -> (TOP) || Control a given sprite with user or simulated input.

''slot'' refers to the sprite to control (0 thru 7) and ''input'' is the input state or simulated input state to send to the sprite.

The given sprite will have a movement animation queued on it if and only if the space for the sprite to move to is free. Otherwise, no action will be taken. Queued sprite animations can be played with other SPR opcodes.

Consult [[#op_A1D|WININPUT]] for information about the format of input state.
|- id='op_3269'
| SPRCHOREO <br> (SPRite CHOREOgraphy) || $78 || $3269 || None || file_id, slot (TOP) -> (TOP) || Place a sprite under control of a choreography script.

''file_id'' refers to the BugFS file containing the choreography script and ''slot'' is the sprite to be placed under it's control. The sprite in ''slot'' will have the choreography script installed, and then frozen in place for later execution.

The choreography script will be copied into one of eight choreography script slots. Each slot is 128 bytes max; and lives in an array starting at $2:DC00. This means choreography scripts may not exceed 64 instructions.
|- id='op_2775'
| SPRANIM <br> (SPRite ANIMate) || $6E || $2775 || None || file_id, ctxt_slot, slot (TOP) -> (TOP) || Load an animation into a sprite animation context for a given sprite.

''file_id'' is the BugFS file ID for a sprite animation to play.

''ctxt_slot'' refers to the animation context that will execute the animation script; while ''slot'' refers to the sprite to be animated. Usually both indices are the same; for example, idle-sprite choreography assumes that sprite 5's animations must always be loaded into animation context 5.
|- id='op_2788'
| SPRPOSPLAY <br> (SPRite POSition and PLAY) || $6F || $2788 || None || slot, x, y (TOP) -> (TOP) || Position and then play a previously loaded animation on a given sprite.

''slot'' refers to the sprite being played (0 thru 7). It must already have an animation queued. It's origin will be placed at the coordinates (''x'', ''y'').

Additionally, all active sprite animations will be evaluated for one frame.
|- id='op_27B3'
| SPRPLAY <br> (SPRite PLAY) || $92 || $27B3 || None || slot (TOP) -> (TOP) || Play a previously-loaded animation on a given sprite.

''slot'' refers to the sprite being played (0 thru 7). It must already have an animation queued.

This opcode is not in use in Network Adventure Bugsite.
|- id='op_27D8'
| SPRWAIT <br> (SPRite WAIT) || $C6 || $27D8 || None || slot, should_clear (TOP) -> (TOP) || Wait for sprite animation to finish.

BugVM execution will halt until the given sprite in ''slot'' finishes animating. Optionally, if ''should_clear'' is TRUE, then we will also clear any deactivated sprites from the screen.
|- id='op_27D8'
| SPRWAITALL <br> (SPRite WAIT ALL) || $79 || $27BB || None || None || Wait for all sprite animations to finish.

BugVM execution will halt until all sprite animations finish, then any deactivated sprites will be cleared from the screen.

This opcode is not in use in Network Adventure Bugsite.
|- id='op_A29'
| SPRINPUT <br> (SPRite INPUT) || $61 || $A29 || None || (TOP) -> input_changed (TOP) || Wait for user input.

BugVM execution will halt until the user presses any button on the system. Sprite animations will continue to execute during this period of halted execution.

Consult [[#op_A1D|WININPUT]] for information about this opcode's output format.
|- id='op_A39'
| SPRHOLD <br> (SPRite HOLD) || $D2 || $A39 || None || (TOP) -> input_held (TOP) || Wait for user input.

BugVM execution will halt until the user presses, or is already holding, any button on the system. Sprite animations will continue to execute during this period of halted execution.

Consult [[#op_A1D|WININPUT]] for information about this opcode's output format.
|- id='op_2386'
| SPRFINISH <br> (SPRite FINISH) || $A7 || $2386 || None || None || Wait for sprites to finish moving.

BugVM execution will halt until all sprites have finished moving.
|- id='op_2877'
| SPRHIDE <br> (SPRite HIDE) || $CF || $2877 || None || slot (TOP) -> (TOP) || Deactivate sprite in ''slot''.
|- id='op_289C'
| SPRWIPE <br> (SPRite WIPE) || $8E || $289C || None || None || Deactivate all sprites and clear them from the screen.
|- id='op_32C7'
| SPRFREEZE <br> (SPRite FREEZE) || $CB || $32C7 || None || slot (TOP) -> (TOP) || Manually freeze sprite in ''slot''.

This opcode is not in use in Network Adventure Bugsite.
|- id='op_32D5'
| SPRTHAW <br> (SPRite THAW) || $CB || $32D5 || None || slot (TOP) -> (TOP) || Manually unfreeze sprite in ''slot''.

This does not revert the freeze caused by [[#op_3269|SPRCHOREO]] - SPRFREEZE and SPRCHOREO freezes are treated separately.

This opcode is not in use in Network Adventure Bugsite.
|}

=== Attribute Table Utilities ===

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_165A'
| PRKEY <br> (PRint KEY item) || $9F || $165A || None || attr_index (TOP) -> (TOP) || Read the given Key Item's Attribute Table block and print it's name.
|- id='op_42A'
| BLKKEY <br> (BLocK KEY item) || $A0 || $42A || None || attr_index (TOP) -> (TOP) || Read the given Key Item's Attribute Table block into W_Battle_AttrStaging.
|- id='op_1668'
| PRMOVE <br> (PRint MOVE) || $A1 || $1668 || None || attr_index (TOP) -> (TOP) || Read the given Battle Move's Attribute Table block and print it's name.
|- id='op_3FE'
| BLKMOVE <br> (BLocK MOVE) || $A2 || $3FE || None || attr_index (TOP) -> (TOP) || Read the given Battle Move's Attribute Table block into W_Battle_AttrStaging.
|- id='op_1622'
| PRMON <br> (PRint MONster) || $AF || $1622 || None || attr_index (TOP) -> (TOP) || Read the given Bug's Attribute Table block and print it's name.
|- id='op_39C'
| BLKMON <br> (BLocK MONster) || $BB || $39C || None || attr_index (TOP) -> (TOP) || Read the given Bug's Attribute Table block into W_Battle_AttrStaging.

This instruction switches between two different Attribute Tables based on the value of W_System_GameVersion.
|- id='op_1661'
| PRCHIP <br> (PRint CHIP) || $E3 || $1661 || None || attr_index (TOP) -> (TOP) || Read the given Chip's Attribute Table block and print it's name.
|- id='op_456'
| BLKCHIP <br> (BLocK CHIP) || $E2 || $456 || None || attr_index (TOP) -> (TOP) || Read the given Chip's Attribute Table block into W_Battle_AttrStaging.
|- id='op_3CD'
| BLKENC <br> (BLocK ENCounter) || $F1 || $3CD || None || attr_index (TOP) -> (TOP) || Read the given Encounter's Attribute Table block into W_Battle_AttrStaging.

There does not appear to be a PRENC instruction.

This instruction switches between two different Attribute Tables based on the value of W_System_GameVersion.
|- id='op_162A'
| PRNAME <br> (PRint NAME) || $A5 || $162A || None || None || Print the name of the currently loaded Attribute Table block.

All PRint instructions that reference Attribute Table data execute this opcode. It prints data from $CF30, which is an offset into W_Battle_AttrStaging that appears to be a standard offset for this kind of data.
|- id='op_1670'
| PRNICK <br> (PRint NICKname) || $E5 || $1638 || None || None || Print the name of the currently loaded Nickname block.

Like PRNAME, this opcode prints the name section of a datablock. However, it prints data stored in the Nickname datablock area, $CC30, which is an offset into the W_NameInput_NicknameDataBlock area. The name "nickname data block area" is assumed; it is not currently known what semantic purpose this area serves other than use by the naming screens.
|}

=== Variable Width Font Rendering ===

These opcodes are exclusive to the English patch of Bugsite and represent new opcodes. They overlap existing ENOP instructions starting from $1F and thus can only be used if you are using BugTools' auto-optimize feature to remove existing ENOP instructions.

{| class='wikitable'
|-
! Opcode !! Encoding(s) !! Native Impl. !! Operand Args !! Stack Args !! Description
|- id='op_VWFCONFIG'
| VWFCONFIG <br> (VWF CONFIG) || $1F || (varies) || None || font, metrics, bg (TOP) -> (TOP) || Configure the font used for VWF text rendering.

''font'' and ''metrics'' refers to the file IDs of the font character data and metrics data, respectively. Character data is stored similarly to FWF fonts, but left-aligned; while metrics data is an array of one byte per character indicating width of each character.

This instruction only configures the font in use by VWF; it does not enable VWF.
|- id='op_VWFENABLE'
| VWFENABLE <br> (VWF ENABLE) || $20 || (varies) || None || ring_start, ring_end (TOP) -> (TOP) || Enable VWF rendering.

When enabled, [[#op_A84|PRINT]] instructions will use the VWF font rendering path. A font should have already been configured via VWFCONFIG before enabling VWF.

''ring_start'' and ''ring_end'' are a range of tiles to use for VWF rendering. Tiles from $100 onward indicate tiles in the second VRAM bank. This range of tiles will constitute a ring buffer of free tiles to be overwritten with VWF text, with drawn tiles starting from the first tile in the ring. Most importantly, new text will overwrite old tiles if the ring runs out of space, so you must ensure text that you don't intend to overwrite occupies it's own rings.
|- id='op_VWFDISABLE'
| VWFDISABLE <br> (VWF DISABLE) || $21 || (varies) || None || None || Disable VWF rendering.

Rendering will return to tile based fonts, using the same tiles normally used for tile text. Note that if you have overwritten these tiles, you will need to reload the FWF font equivalents.
|}