Addressing Modes Addressing opcode operand address field 00000001

Addressing Modes �������

Addressing opcode operand (address field) **** 00000001 01011100 00000010 00001111 00000011 11110000 location content • �������� address �� instruction ����������������

Immediate Addressing • ������� – ������� operand ���������� address Instruction • ���� 1011001 • Operand = 1011001 2(1318) (89(10

Direct Addressing Instruction A Memory Operand • ������� address ���� effective address ��� operand EA = A • Effective address (EA) ��� address ���� location ����� operand – ���� EA ���� address

Direct Addressing 0

Direct Addressing location 000 010 content 111 000 010 001 • EA = page ��� location + offset 000 012 + 0 000 1112 000 010 000 111(80207) 2

Direct Addressing

Direct Addressing • ������ direct ����� PDP 8 ����������� 4 ������� 0 ����������� 5 ������ 0 ������ page ��� 0 location content • ������� TAD 108 ����� location 000 001 000 010 000 100 ��� 02048 TAD(001) direct mode(0) zero page(0) offset(0 001 000)

Direct Addressing location 000 010 content 000 001 • EA = page ��� 0 + offset 000 002 + 0 001 0002 000 001 000(80010) 2

Direct Addressing

Direct Addressing • (x) ��� content ��� location ��� x • ������� operand = (EA) – TAD 2078 • Operand = (02078) = 00228 – TAD 108 • Operand = (00108) = 00178

Indirect addressing • ����� – ������ address ����� location ������ location ��������� Instruction Memory address ����� A Operand

Indirect addressing • ������ indirect ����� PDP 8 ����������� 4 ������� 1 ����������� 5 ������ 1 ������ current page location content • ������� TAD 6108 ����� location 000 001 110 001 000 010 000 100 ��� 02048 TAD(001) indirect mode(1) current page(1) offset(0 001 000)

Indirect addressing location 000 010 000 100 content 000 001 110 001 • A = page ��� location + offset 000 012 + 0 001 0002 000 010 001 000(80210) 2

Indirect addressing

Indirect addressing • EA = (A) • EA = (02108) • EA = 05128 (000 101 0102) Page ��� 2

Indirect addressing

Indirect addressing • Operand = (EA) = (05128) = 33338

����� • William Stalling, Computer Organization and Architecture, USA • Yale N. Patt, Sanjay J. Patel, Introduction to Computing Systems: From Bits and Gates to C and Beyond, USA