## Uxntal Opcodes

Uxn has 64kb of memory, 16 devices, 2 stacks of 255 bytes, 5-bits opcodes and 3 modes. The list below show the standard opcodes and their effect on a given stack **a b c**, **PC**: Program Counter, **[M]**: Memory, **[D+*]**: Device Memory, and **R**: Return/Working Stack.

LIT~ [PC]JCI~ (c8){PC+=[PC]}JMI~ {PC+=[PC]}JSI~ {R.PC PC+=[PC]}BRK~EQUa b==cLDZa b [c8]ADDa b+cINCa b c+1NEQa b!=cSTZa {[c8]=b}SUBa b-cPOPa bGTHa b>cLDRa b [PC+c8]MULa b*cNIPa cLTHa b<cSTRa {[PC+c8]=b}DIVa b/cSWPa c bJMPa b {PC+=c}LDAa b [c16]ANDa b&cROTb c aJCNa (b8){PC+=c}STAa {[c16]=b}ORAa b|cDUPa b c cJSRa b {R.PC PC+=c}DEIa b {[D+c8]}EORa b^cOVRa b c bSTHa b {R.c}DEOa {[D+c8]=b}SFTa b>>c8l<<c8h

To learn more about each opcode, see the Opcode Reference.

## The Uxntal Opcode Reference

This documentation includes hand gestures, and glyphs, which might serve a dual purpose; both enabling the usage of Uxntal outside of the computer, as well as to help students to familiarize themselves with hexadecimal finger-counting and bitwise operations.

00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 0a | 0b | 0c | 0d | 0e | 0f | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

00 | BRK | INC | POP | NIP | SWP | ROT | DUP | OVR | EQU | NEQ | GTH | LTH | JMP | JCN | JSR | STH |

10 | LDZ | STZ | LDR | STR | LDA | STA | DEI | DEO | ADD | SUB | MUL | DIV | AND | ORA | EOR | SFT |

20 | JCI | INC2 | POP2 | NIP2 | SWP2 | ROT2 | DUP2 | OVR2 | EQU2 | NEQ2 | GTH2 | LTH2 | JMP2 | JCN2 | JSR2 | STH2 |

30 | LDZ2 | STZ2 | LDR2 | STR2 | LDA2 | STA2 | DEI2 | DEO2 | ADD2 | SUB2 | MUL2 | DIV2 | AND2 | ORA2 | EOR2 | SFT2 |

40 | JMI | INCr | POPr | NIPr | SWPr | ROTr | DUPr | OVRr | EQUr | NEQr | GTHr | LTHr | JMPr | JCNr | JSRr | STHr |

50 | LDZr | STZr | LDRr | STRr | LDAr | STAr | DEIr | DEOr | ADDr | SUBr | MULr | DIVr | ANDr | ORAr | EORr | SFTr |

60 | JSI | INC2r | POP2r | NIP2r | SWP2r | ROT2r | DUP2r | OVR2r | EQU2r | NEQ2r | GTH2r | LTH2r | JMP2r | JCN2r | JSR2r | STH2r |

70 | LDZ2r | STZ2r | LDR2r | STR2r | LDA2r | STA2r | DEI2r | DEO2r | ADD2r | SUB2r | MUL2r | DIV2r | AND2r | ORA2r | EOR2r | SFT2r |

80 | LIT | INCk | POPk | NIPk | SWPk | ROTk | DUPk | OVRk | EQUk | NEQk | GTHk | LTHk | JMPk | JCNk | JSRk | STHk |

90 | LDZk | STZk | LDRk | STRk | LDAk | STAk | DEIk | DEOk | ADDk | SUBk | MULk | DIVk | ANDk | ORAk | EORk | SFTk |

a0 | LIT2 | INC2k | POP2k | NIP2k | SWP2k | ROT2k | DUP2k | OVR2k | EQU2k | NEQ2k | GTH2k | LTH2k | JMP2k | JCN2k | JSR2k | STH2k |

b0 | LDZ2k | STZ2k | LDR2k | STR2k | LDA2k | STA2k | DEI2k | DEO2k | ADD2k | SUB2k | MUL2k | DIV2k | AND2k | ORA2k | EOR2k | SFT2k |

c0 | LITr | INCkr | POPkr | NIPkr | SWPkr | ROTkr | DUPkr | OVRkr | EQUkr | NEQkr | GTHkr | LTHkr | JMPkr | JCNkr | JSRkr | STHkr |

d0 | LDZkr | STZkr | LDRkr | STRkr | LDAkr | STAkr | DEIkr | DEOkr | ADDkr | SUBkr | MULkr | DIVkr | ANDkr | ORAkr | EORkr | SFTkr |

e0 | LIT2r | INC2kr | POP2kr | NIP2kr | SWP2kr | ROT2kr | DUP2kr | OVR2kr | EQU2kr | NEQ2kr | GTH2kr | LTH2kr | JMP2kr | JCN2kr | JSR2kr | STH2kr |

f0 | LDZ2kr | STZ2kr | LDR2kr | STR2kr | LDA2kr | STA2kr | DEI2kr | DEO2kr | ADD2kr | SUB2kr | MUL2kr | DIV2kr | AND2kr | ORA2kr | EOR2kr | SFT2kr |

In the

notation, "a b" represent the state of the stack before the operation, "c d" represent the state after the operation, with "b" and "d" on top of the stack, respectively.`a b -- c d`

### Break

`BRK `

Ends the evalutation of the current vector. This opcode has no modes.`--`

### Jump Conditional Instant

`JCI `

Pops a byte from the working stack and if it is not zero, moves the PC to a relative address at a distance equal to the next short in memory, otherwise moves PC+2. This opcode has no modes.
`cond8 -- `

### Jump Instant

`JMI `

Moves the PC to a relative address at a distance equal to the next short in memory. This opcode has no modes.
` -- `

### Jump Stash Return Instant

`JSI `

Pushes PC+2 to the return-stack and moves the PC to a relative address at a distance equal to the next short in memory. This opcode has no modes.
` -- `

### Literal

`LIT `

Pushes the next bytes in memory, and moves the PC+2. The LIT opcode always has the keep mode active. Notice how the `-- a`

`0x00`

opcode, with the *keep* bit toggled, is the location of the literal opcodes. To learn more, see literals.

LIT 12 ( 12 ) LIT2 abcd ( ab cd )

### Increment

`INC `

Increments the value at the top of the stack, by 1.`a -- a+1`

#01 INC ( 02 ) #0001 INC2 ( 00 02 ) #0001 INC2k ( 00 01 00 02 )

### Pop

`POP `

Removes the value at the top of the stack.`a --`

#1234 POP ( 12 ) #1234 POP2 ( ) #1234 POP2k ( 12 34 )

### Nip

`NIP `

Removes the second value from the stack. This is practical to convert a short into a byte.`a b -- b`

#1234 NIP ( 34 ) #1234 #5678 NIP2 ( 56 78 ) #1234 #5678 NIP2k ( 12 34 56 78 56 78 )

### Swap

`SWP `

Exchanges the first and second values at the top of the stack.`a b -- b a`

#1234 SWP ( 34 12 ) #1234 SWPk ( 12 34 34 12 ) #1234 #5678 SWP2 ( 56 78 12 34 ) #1234 #5678 SWP2k ( 12 34 56 78 56 78 12 34 )

### Rotate

`ROT `

Rotates three values at the top of the stack, to the left, wrapping around.`a b c -- b c a`

#1234 #56 ROT ( 34 56 12 ) #1234 #56 ROTk ( 12 34 56 34 56 12 ) #1234 #5678 #9abc ROT2 ( 56 78 9a bc 12 34 ) #1234 #5678 #9abc ROT2k ( 12 34 56 78 9a bc 56 78 9a bc 12 34 )

### Duplicate

`DUP `

Duplicates the value at the top of the stack.`a -- a a`

#1234 DUP ( 12 34 34 ) #12 DUPk ( 12 12 12 ) #1234 DUP2 ( 12 34 12 34 )

### Over

`OVR `

Duplicates the second value at the top of the stack.`a b -- a b a`

#1234 OVR ( 12 34 12 ) #1234 OVRk ( 12 34 12 34 12 ) #1234 #5678 OVR2 ( 12 34 56 78 12 34 ) #1234 #5678 OVR2k ( 12 34 56 78 12 34 56 78 12 34 )

### Equal

`EQU `

Pushes 01 to the stack if the two values at the top of the stack are equal, 00 otherwise.`a b -- bool8`

#1212 EQU ( 01 ) #1234 EQUk ( 12 34 00 ) #abcd #ef01 EQU2 ( 00 ) #abcd #abcd EQU2k ( ab cd ab cd 01 )

### Not Equal

`NEQ `

Pushes 01 to the stack if the two values at the top of the stack are not equal, 00 otherwise.`a b -- bool8`

#1212 NEQ ( 00 ) #1234 NEQk ( 12 34 01 ) #abcd #ef01 NEQ2 ( 01 ) #abcd #abcd NEQ2k ( ab cd ab cd 00 )

### Greater Than

`GTH `

Pushes 01 to the stack if the second value at the top of the stack is greater than the value at the top of the stack, 00 otherwise.`a b -- bool8`

#1234 GTH ( 00 ) #3412 GTHk ( 34 12 01 ) #3456 #1234 GTH2 ( 01 ) #1234 #3456 GTH2k ( 12 34 34 56 00 )

### Lesser Than

`LTH `

Pushes 01 to the stack if the second value at the top of the stack is lesser than the value at the top of the stack, 00 otherwise.`a b -- bool8`

#0101 LTH ( 00 ) #0100 LTHk ( 01 00 00 ) #0001 #0000 LTH2 ( 00 ) #0001 #0000 LTH2k ( 00 01 00 00 00 )

### Jump

`JMP `

Moves the PC by a relative distance equal to the signed byte on the top of the stack, or to an absolute address in short mode.`addr --`

,&skip-rel JMP BRK &skip-rel #01 ( 01 )

### Jump Conditional

`JCN `

If the byte preceeding the address is not 00, moves the PC by a signed value equal to the byte on the top of the stack, or to an absolute address in short mode.`cond8 addr --`

#abcd #01 ,&pass JCN SWP &pass POP ( ab ) #abcd #00 ,&fail JCN SWP &fail POP ( cd )

### Jump Stash Return

`JSR `

Pushes the PC to the return-stack and moves the PC by a signed value equal to the byte on the top of the stack, or to an absolute address in short mode.`addr --`

,&get JSR #01 BRK &get #02 JMP2r ( 02 01 )

### Stash

`STH `

Moves the value at the top of the stack, to the return stack.`a --`

#01 STH LITr 02 ADDr STHr ( 03 )

### Load Zero-Page

`LDZ `

Pushes the value at an address within the first 256 bytes of memory, to the top of the stack.`addr8 -- value`

|00 @cell $2 |0100 .cell LDZ ( 00 )

### Store Zero-Page

`STZ `

Writes a value to an address within the first 256 bytes of memory.`val addr8 --`

|00 @cell $2 |0100 #abcd .cell STZ2 { ab cd }

### Load Relative

`LDR `

Pushes a value at a relative address in relation to the PC, within a range between -128 and +127 bytes, to the top of the stack.`addr8 -- value`

,cell LDR2 BRK @cell abcd ( ab cd )

### Store Relative

`STR `

Writes a value to a relative address in relation to the PC, within a range between -128 and +127 bytes.`val addr8 --`

#1234 ,cell STR2 BRK @cell $2 ( )

### Load Absolute

`LDA `

Pushes the value at a absolute address, to the top of the stack.`addr16 -- value`

;cell LDA BRK @cell abcd ( ab )

### Store Absolute

`STA `

Writes a value to a absolute address.`val addr16 --`

#abcd ;cell STA BRK @cell $1 ( ab )

### Device Input

`DEI `

Pushes a value from the device page, to the top of the stack. The target device might capture the reading to trigger an I/O event.`device8 -- value`

### Device Output

`DEO `

Writes a value to the device page. The target device might capture the writing to trigger an I/O event.`val device8 --`

### Add

`ADD `

Pushes the sum of the two values at the top of the stack.`a b -- a+b`

#1a #2e ADD ( 48 ) #02 #5d ADDk ( 01 5d 5f ) #0001 #0002 ADD2 ( 00 03 )

### Subtract

`SUB `

Pushes the difference of the first value minus the second, to the top of the stack.`a b -- a-b`

### Multiply

`MUL `

Pushes the product of the first and second values at the top of the stack.`a b -- a*b`

### Divide

`DIV `

Pushes the quotient of the first value over the second, to the top of the stack.`a b -- a/b`

### And

`AND `

Pushes the result of the bitwise operation AND, to the top of the stack.`a b -- a&b`

### Or

`ORA `

Pushes the result of the bitwise operation OR, to the top of the stack.`a b -- a|b`

### Exclusive Or

`EOR `

Pushes the result of the bitwise operation XOR, to the top of the stack.`a b -- a^b`

### Shift

`SFT `

Shifts the bits of the second value of the stack to the left or right, depending on the control value at the top of the stack. The high nibble of the control value indicates how many bits to shift left, and the low nibble how many bits to shift right. The rightward shift is done first.`a shift8 -- c`

#34 #10 SFT ( 68 ) #34 #01 SFT ( 1a ) #34 #33 SFTk ( 34 33 30 ) #1248 #34 SFTk2 ( 12 48 34 09 20 )

- Rekka Bellum, illustration
- Kira Oakley, contributor
- Ismael Venegas Castello, contributor