EE101Lecture26

EE101Lecture26 - Mark Redekopp, All rights reserved...

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Unformatted text preview: Mark Redekopp, All rights reserved Introduction to Digital Logic Lecture 26 Simple CPU HW Design Mark Redekopp, All rights reserved Our 8-bit Computer 8-bit data and addresses but 16-bit instructions I/O 8-bit input data from keyboard 8 LEDs for output display Memory Store program instructions For our design well use a separate 256x16 instruction memory (256 rows / instructions each being 16-bits) Stores program data For our design well use a separate 128x8 data memory (each data element is a byte-size value Registers Temporary storage locations inside processor for fast access For our design well use (16) 8-bit registers: R0-RF Mark Redekopp, All rights reserved Data Address Space With 8-bit values we can make 256 unique addresses Address range: 00-FF hex We said our data memory will only have 128 locations Address range: 00 7F hex What about the other 128? We will map our I/O devices to some of those unused addresses Read of address 80 hex will return keyboard data Write of address 80 hex will output to LEDs FF Memory 7F 80 128 x 8 RAM I/O and Unused Space Keyboard (Read) / LEDs (Write) 81 Unoccupied / Unused Mark Redekopp, All rights reserved Instruction Set Processor supports 11 instructions Instruction Type Comment ADD Rd,Rs,Rt Rd = Rs + Rt SUB Rd,Rs,Rt Rd = Rs Rt MOVE Rd,Rs Rd = Rs XOR Rd,Rs,Rt Rd = Rs XOR Rt AND Rd,Rs,Rt Rd = Rs AND Rt OR Rd,Rs,Rt Rd = Rs OR Rt JEQZ Rt,WX If(Rt = 0) jump to instruc. At address WXIf(Rt = 0) jump to instruc....
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EE101Lecture26 - Mark Redekopp, All rights reserved...

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