ADD Rdst, Rsrc1, Rsrc2

      MAR <- PC, PC <- PC+1
      MDR <- MEM[MAR]
      IR <- MDR
      DECODE
      GPR[IR[11:9]] <- GPR[IR[8:6]] + GPR[IR[2:0]], setCC()

LD:
      MAR <- PC, PC <- PC + 1
      MDR <- MEM[MAR]
      IR <- MDR
      DECODE
      MAR <- PC + sext(IR[8:0])
      MDR <- MEM[MAR]
      GPR[IR[11:9]] <- MDR, setCC()

STR:
      MAR <- PC, PC <- PC + 1
      MDR <- MEM[MAR]
      IR <- MDR
      DECODE
      MAR <- GPR[IR[8:6]] + sext(IR[5:0])
      MDR <- GPR[IR[11:9]]
      MEM[MAR] <- MDR

JSR:
      MAR <- PC, PC <- PC + 1
      MDR <- MEM[MAR]
      IR <- MDR
      DECODE
      R7 <- PC
      PC <- PC + sext(IR[10:0])