instruction encoding

control word encoding:
---------------------------------------------------------------------------------------------------------------------------------
|   00  |   01  |   02  |   03  |   04  |   05  |   06  |   07  |   08  |   09  |   10  |   11  |   12  |   13  |   14  |   15  |
|-------------------------------------------------------------------------------------------------------------------------------|
|                                                           Registers                                                           |
|-------------------------------------------------------------------------------------------------------------------------------|
|       $x      |       $y      |       PC      |  CIR  |  MAR  |      MDR      |  Run  |  Opc  |       BP      |       SP      |
|-------------------------------------------------------------------------------------------------------------------------------|
|   I   |   O   |   I   |   O   |   I   |   O   |   I   |   I   |   I   |   O   |   I   |   O   |   I   |   O   |   I   |   O   |
---------------------------------------------------------------------------------------------------------------------------------


---------------------------------------------------------------------------------------------------------------------------------
|   16  |   17  |   18  |   19  |   20  |   21  |   22  |   23  |   24  |   25  |   26  |   27  |   28  |   29  |   30  |   31  |
|-------------------------------------------------------------------------------------------------------------------------------|
|   ALU inputs  |                                              ALU outputs                                              |       |
|-----------------------------------------------------------------------------------------------------------------------|       |
|   1   |   2   |  add  |  sub  |  inc  |  dec  |  not  |  and  |   or  |  xor  |  slt  |  srl  |  mult |  div  |  rem  |  end  |
|-----------------------------------------------------------------------------------------------------------------------|       |
|   I   |   I   |   O   |   O   |   O   |   O   |   O   |   O   |   O   |   O   |   O   |   O   |   O   |   O   |   O   |       |
---------------------------------------------------------------------------------------------------------------------------------


bank[x] is shorthand for mem[$$bp * 16 + x]

add $x, $y
encoding: 000000XY
description: $x += $y
microcode:
xo alu1
yo alu2
add xi end
01000000000000001000000000000000
00010000000000000100000000000000
10000000000000000010000000000001

sub $x, $y
encoding: 000001XY
description: $x -= $y
microcode:
xo alu1
yo alu2
sub xi end
01000000000000001000000000000000
00010000000000000100000000000000
10000000000000000001000000000001

halt
encoding: 00001000
description: Stop execution

rst
encoding: 00001001
description: Set all the registers to 0, clear memory after program

brk $x
encoding: 0000101X
description: Write $x to the continuously-displayed 1-byte breakpoint buffer
             (and then start stepping through execution?)

inc $x
encoding: 0000110X
description: $x ++
microcode:
xo alu1
inc xi end
01000000000000001000000000000000
10000000000000000000100000000001

dec $x
encoding: 0000111X
description: $x --
microcode:
xo alu1
dec xi end
01000000000000001000000000000000
10000000000000000000010000000001

not $x, $y
encoding: 000100XY
description: $x = ~$y
microcode:
xo alu1
not xi end
01000000000000001000000000000000
10000000000000000000001000000001

and $x, $y
encoding: 000101XY
description: $x &= $y
microcode:
xo alu1
and xi end
01000000000000001000000000000000
10000000000000000000000100000001

or $x, $y
encoding: 000110XY
description: $x |= $y
microcode:
xo alu1
or xi end
01000000000000001000000000000000
10000000000000000000000010000001

xor $x, $y
encoding: 000111XY
description: $x ^= $y
microcode:
xo alu1
xor xi end
01000000000000001000000000000000
10000000000000000000000001000001

li $x, imm
encoding: 001XIIII
description: $x = imm
microcode:
opco xi end
10000000000100000000000000000001

slt $x, $y
encoding: 010000XY
description: $x = ($x < $y)
microcode:
xo alu1
yo alu2
slt xi end
01000000000000001000000000000000
00010000000000000100000000000000
10000000000000000000000000100001

srl $x, $y
encoding: 010001XY
description: $x >>= $y ($y signed)
microcode:
xo alu1
yo alu2
srl xi end
01000000000000001000000000000000
00010000000000000100000000000000
10000000000000000000000000010001

mult $x, $y
encoding: 010010XY
description: $x *= $y
microcode:
xo alu1
yo alu2
mult xi end
01000000000000001000000000000000
00010000000000000100000000000000
10000000000000000000000000001001

div $x, $y
encoding: 010011XY
description: $x /= $y
microcode:
xo alu1
yo alu2
div xi
rem yi end
01000000000000001000000000000000
00010000000000000100000000000000
10000000000000000000000000000100
00100000000000000000000000000011

j imm
encoding: 0101IIII
description: $$pc = imm
microcode:
bpo opco pci end
00001000000101000000000000000001

jnez $x, imm
encoding: 011XIIII
description: if ($x) $$pc = imm
microcode:
bpo opco pci end
00001000000101000000000000000001

lw $x, [imm]
encoding: 100XIIII
description: $x = bank[imm]
microcode:
bpo opco mari
mdro xi end
00000001000101000000000000000000
10000000010000000000000000000001

sw $x, [imm]
encoding: 101XIIII
description: bank[imm] = $x
microcode:
bpo opco mari
xo mdri end
00000001000101000000000000000000
01000000100000000000000000000001

lw $x, [$y]
encoding: 110000XY
description: $x = mem[$y]
microcode:
yo mari
mdro xi end
00010001000000000000000000000000
10000000010000000000000000000001

sw $x, [$y]
encoding: 110001XY
description: mem[$y] = $x
microcode:
yo mari
xo mdri end
00010001000000000000000000000000
01000000100000000000000000000001

copy [$x], [$y]
encoding: 110010XY
description: mem[$x] = mem[$y]
microcode:
yo mari
mdro yi
xo mari
yo mdri end
00010001000000000000000000000000
00100000010000000000000000000000
01000001000000000000000000000000
00010000100000000000000000000001

swap [$x], [$y]
encoding: 110011XY
description: tmp = mem[$x]; mem[$x] = mem[$y]; mem[$y] = tmp
microcode:
yo mari
mdro alu1 alu2
xo mari
mdro xi
and mdri
yo mari
xo mdri end
00010001000000000000000000000000
00000000010000001100000000000000
01000001000000000000000000000000
10000000010000000000000000000000
00000000100000000000000100000000
00010001000000000000000000000000
01000000100000000000000000000001

push $x
encoding: 1101000X
description: mem[$$sp] = $x; $$sp ++
microcode:
spo mari alu1
xo mdri
inc spi end
00000001000000011000000000000000
01000000100000000000000000000000
00000000000000100000100000000001

pop $x
encoding: 1101001X
description: $x = mem[$$sp]; $$sp --
microcode:
spo alu1
dec spi mari
mdro xi end
00000000000000011000000000000000
00000001000000100000010000000000
10000000010000000000000000000001

call $x
encoding: 1101010X
description: mem[$$sp] = $$pc; $$sp ++; $$pc = $x
microcode:
spo mari alu1
pco mdri
inc spi
xo pci end
00000001000000011000000000000000
00000100100000000000000000000000
00000000000000100000100000000000
01001000000000000000000000000001

init
encoding: 11010110
description: $$sp = &bank[0] OR $$sp = $$bp * 16
microcode:
bpo spi end
00000000000001100000000000000001

rts
encoding: 11010111
description: $$pc = mem[$$sp]; $$sp --;
microcode:
spo alu1
dec spi mari
mdro pci end
00000000000000011000000000000000
00000001000000100000010000000000
00001000010000000000000000000001

push [$x$y]
encoding: 110110XY
description: mem[$$sp] = mem[$x * 16 + $y]; $$sp ++

pop [$x$y]
encoding: 110111XY
description: mem[$x$y] = mem[$$sp]; $$sp --

bnk $x
encoding: 1110000X
description: $$bp = $x
microcode:
xo bpi end
01000000000010000000000000000001

incb
encoding: 11100010
description: $$bp ++
microcode:
bpo alu1
inc bpi end
00000000000001001000000000000000
00000000000010000000100000000001

decb
encoding: 11100011
description: $$bp --
microcode:
bpo alu1
dec bpi end
00000000000001001000000000000000
00000000000010000000010000000001

addb $x
encoding: 1110010X
description: $$bp += $x
microcode:
bpo alu1
xo alu2
add bpi end
00000000000001001000000000000000
01000000000000000100000000000000
00000000000010000010000000000001

subb $x
encoding: 1110011X
description: $$bp -= $x
microcode:
bpo alu1
xo alu2
sub bpi end
00000000000001001000000000000000
01000000000000000100000000000000
00000000000010000001000000000001

bnki imm
encoding: 11101III
description: $$bp = imm
microcode:
opco bpi end
00000000000110000000000000000001

IO stuff:

???
encoding: 111100XY

???
encoding: 111101XY

???
encoding: 111110XY

???
encoding: 111111XY