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Instruction Set

Arithmetic & Logic instructions

  • NOP 0000 0000 0000 0000

No operation

  • ADD 0000 0001 00cc aabb

W[cc] = W[aa] + W[bb]
If overflow occurs, register CR bit OV is set.

  • SUB 0000 0010 00cc aabb

W[cc] = W[aa] - W[bb]

  • AND 0000 0011 00cc aabb

Bitwise AND

W[cc] = W[aa] AND W[bb]

  • OR 0000 0100 00cc aabb

Bitwise OR

W[cc] = W[aa] OR W[bb]

  • XOR 0000 0101 00cc aabb

Bitwise XOR

W[cc] = W[aa] XOR W[bb]

  • INC 0000 0110 0000 00aa

W[aa] = W[aa] + 1 If overflow occur, ignore carry bit.

  • DEC 0000 0111 0000 00aa

W[aa] = W[aa] - 1

  • SET 0000 1000 aayy xxxx

Set 4 bits of register W[aa] with xxxx.
Remaining bits are unchanged.
The bits are selected with yy:

yy=00 -> W[aa][0-3]
yy=01 -> W[aa][4-7]
yy=10 -> W[aa][8-11]
yy=11 -> W[aa][12-15]

  • CLR 0000 1010 0000 00aa

Clear register W[aa]

  • NOT 0000 1011 0000 00aa

W[aa] = ~W[aa] Bitwise NOT operation on register W[aa].

Branch instructions

  • JMP 1000 0000 0000 00aa

Set IP = W[aa].

  • BRE 1000 0010 00cc aabb

If W[aa] == W[bb], then set IP = W[cc].

  • BRNE 1000 0011 00cc aabb

If W[aa] != W[bb], then set IP = W[cc].

  • BRL 1000 0100 00cc aabb

If W[aa] < W[bb], then set IP = W[cc].

  • BRH 1000 0101 00cc aabb

If W[aa] > W[bb], then set IP = W[cc].

  • BRNZ 1000 1001 0000 ccaa

If W[aa] != 0, then set IP = W[cc].

  • CALL 1000 0110 0000 00aa

Performs a function call:

SP = SP + 2
*SP = IP
IP = W[aa]

  • RET 1000 0111 0000 0000

Returns from a function call

IP = *SP
SP = SP - 2

  • RETI 1000 1000 0000 0000

Same as RET, but also sets the GLE flag on the CR register.

Memory instructions

  • LD W[aa] W[bb] 0100 0001 0000 aabb

Load contents of memory address given by W[aa], on the bank selected on BK into the register W[bb].

W[bb] = MEMORY[W[aa]]

  • ST W[aa] W[bb] 0100 0010 0000 aabb

Store the contents of W[bb] in address given by W[aa], on the bank selected on BK.

MEMORY[W[aa]] = W[bb]

  • CPY 0100 0011 0000 aabb

Copy the contents of register W[aa] to the register W[bb].

  • PUSH 0100 1000 0000 00aa

Push the contents of register W[aa] on the stack:

SP = SP + 2
*SP = W[aa]

  • POP 0100 1001 0000 00aa

Pop a value from top of the stack on register W[aa]:

W[aa] = *SP
SP = SP - 2

  • PEEK 0100 1010 aaxx xxxx

Load the value from address SP - 0bxxxxxx into W[aa]:

W[aa] = *(SP - 0bxxxxxx)

  • CSP 0100 1011 aaxx xxxx

Load the address SP - 0bxxxxxx into W[aa]:

W[aa] = SP - 0bxxxxxx

  • SPXL 0100 1100 0000 aabb

Use the 4 lower bits of W[aa] to set the pixel indexed on the video memory addressed by W[bb]. Note that the video memory is 4-bit addressed, so index are from 0 to 2*last_video_mem_byte.

Control instructions

  • DAI 1100 0000 0000 0000

Disable global interrupt

  • EAI 1100 0001 0000 0000

Enable global interrupt

  • DTI 1100 0010 0000 000a

Disable time interrupt a

  • ETI 1100 0011 0000 000a

Enable time interrupt a

  • SELB 1100 0100 0000 00aa

Select Memory Bank aa in CR register

  • BRK 1111 1110 0000 0000

Breakpoint (software handled) - Mostly used for testing.

  • HLT 1111 1111 0000 0000

Halt system

Pseudo-instructions

  • SETREG W[aa] 0xABCD

Easily sets all bytes of a register

Expands to

SET W[aa] 3 0xA
SET W[aa] 2 0xB
SET W[aa] 1 0xC
SET W[aa] 0 0xD

  • PUSHALL

Push all registers to stack

Expands to

PUSH W0
PUSH W1
PUSH W2
PUSH W3

  • POPALL

Pop all registers from stack

Expands to

POP W3
POP W2
POP W1
POP W0