SAP-2 Instruction Sets

• same fetch cycle (T1, T2, T3) as SAP-1
• memory reference instructions: LDA, STA (3 bytes, lower byte before higher byte)
• immediate instructions: MVI reg, value (2 bytes)
• register instructions: MOV, ADD and SUB, INR and DCR, ANA, ORA, XRA, CMA (1 byte), ANI, ORI, XRI (2 bytes)
• jump and call instructions: JMP, JM, JZ, JNZ, CALL (3 bytes), RET (1 byte)
• CALL saves return address in memory FFFEH and FFFFH
• NOP, HLT, RAL, RAR (1 byte), IN, OUT (2 bytes) 

In-Class Exercise 1

• hand-assemble the following program starting at address 2000H
• op-codes are: “IN” is DBH, "MOV B,A" is 47H, "DCR A" is 3DH, "MOV C,A" is 4FH, "ANA B" is A0H, "MOV A,C" is 79H, JNZ is 79H
• What does the program do? 

START IN 01H

LOOP   MOV B, A

             DCR A

             MOV C, A

             ANA B

             MOV A, C

             JNZ LOOP

DONE

Fig: SAP-2 Instruction Sets