ST2
Definitions
| aaa | 12 bit address |
| kk | 8 bit constant |
| n | 4 bit constant |
| x | Register number Vx (x = 0 to F) |
| y | Register number Vy (y = 0 to F) |
| I | Register I (12 bit) |
| [I] | Memory value of address in register I |
| [Vy] | Memory value of address in register Vy within in page 8 (RAM) |
| 1..9, A..F | Hexadecimal digits |
Syntax
| Opcode | Mnemonic | Parameter | Definition |
|---|---|---|---|
| 7xkk | ADD | Vx, kk | Vx = Vx + kk, x != 0 |
| 8xy4 | ADD | Vx, Vy | Vx = Vx + Vy, VB = carry |
| FxB6 | AFOR | Vx | AND register Vx with F (15), then OR result into least significant byte of register I (used for looking up number graphics), x != 0 |
| 8xy2 | AND | Vx, Vy | Vx = Vx AND Vy, VB undefined |
| 2aaa | CALL | aaa | Call subroutine at aaa (The maximum depth of subroutine call is defined by the 1802 Stack, which grows down into user memory from $880) |
| 70kk | DJNZ | V0, kk | Decrement V0, jump to kk (same page) if register V0 is not zero |
| Dnkk | JKP | n, kk | Check if key number n is pressed, if so store key in RB and jump to kk (same page), n != F |
| DFkk | JKP | VB, kk | Check if key number stored in RB from keypad in RA (1= left, 0 = right) is pressed, if jump to kk (same page) |
| 1aaa | JP | aaa | Jump to address aaa |
| 3xkk | JNZ | Vx, kk | Jump to kk (same page) if register Vx is not zero |
| 4xkk | JZ | Vx, kk | Jump to kk (same page) if register Vx is zero |
| 9xy8 | LD | B, [Vy], Vx B, Vy, Vx |
Store BCD value of Vx in [Vy+800], [Vy+801], [Vy+802], MSB Vx unchanged, Vy will point to last byte of the converted number |
| Aaaa | LD | I, aaa | I = aaa |
| 6xkk | LD | Vx, kk | Vx = kk |
| 8xy0 | LD | Vx, Vy | Vx = Vy, VB undefined |
| 9xy2 | LD | Vx, [Vy] | Vx = [Vy+800] |
| 9xy1 | LD | Vy, Vx | Vy = Vx, VB undefined |
| Bnkk | LD | [I], kk, n [I], kk, +n |
[I] = kk, I = I + n |
| 9xy4 | LD | [Vy], Vx | [Vy+800] = Vx |
| 02F2 | LD | [>I], 0 [I], 0 |
If I contains $Axx fills memory locations $A00 to $Axx (inclusive) with zero. |
| FxA6 | LDM | Vx, [I] | Vx = [I], x != 0 |
| FxA9 | LDM | [I], Vx | [I] = Vx, x != 0 |
| FxAC | LDMA | Vx, [I] | Vx = [I], I = I + 1, x != 0 |
| FxAF | LDMA | [I], Vx | [I] = Vx, I = I + 1, x != 0 |
| 8xy1 | OR | Vx, Vy | Vx = Vx OR Vy, VB undefined |
| C0 | RETURN | Return from subroutine | |
| Cxkk | RND | Vx , kk | Vx = random AND kk, x != 0 |
| FxB3 | SLSB | Vx | Set least significant byte of I to Vx, bit 8 to 11 are unaffected, x != 0 |
| 8xxE | SHL | Vx | Vx = Vx << 1, VB = carry |
| 8xyE | SHL | Vx , Vy | Vx = Vy << 1, VB = carry |
| 8xx6 | SHR | Vx | Vx = Vx >> 1, VB = carry |
| 8xy6 | SHR | Vx , Vy | Vx = Vy >> 1, VB = carry |
| 5xkk | SNE | Vx, kk | Skip next instruction if Vx != kk |
| 9xy0 | SNE | Vx, Vy | Skip next instruction if Vx != Vy |
| E0 | SP | CLEAR | Clear sprite graphic buffer |
| E1 | SP | MOVE | Move sprite |
| E2 | SP | VC, MOVE | Move sprite in direction given in register RC |
| E4 | SP | XOR, [I] | XOR graphic data at register I into sprite graphic buffer |
| E8kk | SP | DRW, JC, kk DRW, kk |
Draw sprite, jump to kk (same page) if a collision occurs |
| 8xy5 | SUB | Vx, Vy | Vx = Vx - Vy, VB = !borrow |
| 8xy7 | SUBN | Vx, Vy | Vx = Vy - Vx, VB = !borrow |
| 0aaa | SYS | aaa | Call CDP1802 code at aaa |
| F0kk | SYS | 2kk | Call CDP1802 code at 2kk |
| 0066 | VIDEO | ON | Turns on the video circuitry. This is actually done in the boot sequence. |
| 8xy3 | XOR | Vx, Vy | Vx = Vx XOR Vy, VB undefined |