The Complete Microprocessor

The Complete Microprocessor - The Complete Microprocessor...

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Unformatted text preview: The Complete Microprocessor Password____None _________ Copyright 2009 Daniel Tylavsky In the previous lecture we looked at defining the contents of our controller PROM by observing the controller outputs needed to enable registers, route data, and control the ALU. In this lecture we will look at: How the controller accesses the PROM contents when a program is executed. How the complete microprocessor executes an example program. The Complete Microprocessor Typically, addresses used to specify memory locations in PROM use Hex codes, with each Hex character representing a 4 bit byte. A2H = 1010 0010 B Because each instruction uses 4 micro- instruction to complete its tasks, it will be convenient to let our least significant Hex character index the micro-instruction using a 2-bit string. A2H = 1010 10 B The Complete Microprocessor PROM 64 Words X 12 Bits 11 10 9 S5 8 S4 7 S3 6 S2 5 S1 4 S0 3 2 1 Hex Addr Instruction 00 Load Acc 10 Add 20 Store To Addr 30 Stop 40 Etc. .. .. F0 ? Each of the instructions in our set requires several tasks to be completed in sequence. Each sequential task is performed by a microinstruction . Look at sequence of Microinstructions to Add then Load Acc . Assume for this exercise each instruction needs 4 clock cycles. PROM 64 Words X 12 Bits . 11 10 S5 9 S4 8 S3 7 S2 6 S1 5 S0 4 3 2 1 Hex Addr Instruction Micro Instr. 00 Load Acc Fetch Instr. 01 2nd Instr. 02 3rd Instr. 03 4th Instr. 10 Add Fetch Instr. 11 2nd Instr. 12 3rd Instr. 13 4th Instr. 20 Store To Addr Fetch Instr. 21 . . . 23 . . . . . . 30 Stop Fetch Instr. 31 . . . 33 . . . . . . 40 Or Fetch Instr. 41 . . . 43 . . . . . . Clear 1 A d d Add Instruction = 1H 1 1 1 1 1 1 1 1 1 L d A c Load Acc Instruction = 0H 1 After One Clock Cycle Delay After One Clock Cycle Delay After One Clock Cycle Delay After One Clock Cycle Delay After One Clock Cycle Delay Another Instr. PROM 64 Words X 12 Bits ....
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The Complete Microprocessor - The Complete Microprocessor...

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