// Main opcodes (op field)
`define OP_LB       6'h20 // Load byte
`define OP_LH       6'h21 // Low half word
`define OP_LW       6'h23 // Load word
`define OP_LBU      6'h24 // Load byte without sign extension (unsigned)
`define OP_LHU      6'h25 // Load .5 word without sign extension
(unsigned)
`define OP_SB       6'h28 // Store a byte and only a byte (don't change
other bytes in the word)
`define OP_SH       6'h29 // Same with half word
`define OP_SW       6'h2b