Computer organization involves fetching instructions from memory and executing them. There are two main approaches to implementing the control unit: hardwired control and microprogrammed control. Hardwired control uses combinational logic to generate control signals based on the instruction and state, while microprogrammed control stores control sequences as microinstructions in a separate control store.

1. Computer organization

2. Organization of control units

8. Performing arithmetic and logic operation Ri Y mux A B ALU z Processor bus select Constant 4

23. Hardwired control Control step counter Step counter External inputs Condition codes Encoder Instruction decoder IR clock End Run INS1 INS n T1

30. Microprogrammed control 3. 1. PC out, MAR in, Read,Select,Add,Zin 2. 0 0 0 0 0 0 1 1 1 0 0 0 1 1 1 0 1. E nd WMFC R3 out R1 in R1 out Z out Z in Add select Y in IR in MDR out Read MAR in PC out PC in Micro instruction

31. Basic organization of a Micro programmed control unit Starting address generator IR μ PC Control store Clock CW

34. Micro programmed control Starting address generator IR μ PC Control store Clock CW External inputs Condition codes

39. Micro instruction sequencing organization μ AR Control store Next address OR gate μ IR Microinstruction decoder Decoding circuit IR Condition codes External inputs Control signals