Instructions. Philipp Koehn. 16 February 2018

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1 Instructions Philipp Koehn 16 February 201 Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

2 1 number adder Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

3 Design Goal 2 Build a machine that adds several numbers together Numbers stored in 64 KB RM Idea: Loop through memory with ripple counter Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

4 64 KB RM 3 16 W DI 64Kx RM DO Read/write bits at a time (one byte) 16 bit address space: 2 16 =65,536 bytes Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

5 Control Panel 4 Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

6 Control Panel 5 Control Panel 16 W DI 64Kx RM DO We can enter numbers and inspect with a control panel Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

7 Ripple Counter 6 OUT0 OUT1 OUT2 OUT3 NOT D D D NOT > CLK > CLK > CLK CLK OUT OUT OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

8 Connecting Ripple Counter to Memory 7 Control Panel Oscillator CLK Ripple Counter O 16 W DI 64Kx RM DO Ripple counter rotates through number 0, 1,... Each clock cycle, a new number is emitted from memory Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

9 dder CO B -BIT DDER S CI dds two numbers: S=+B Overflow: Carry out (CO) Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

10 Latch 9 >CLK D -BIT LTCH -bit memory Edge-triggered: stores value when clock turns to 1 To be used as accumulator Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

11 Connecting dder and Latch 10 DT B -BIT DDER CO S CI CLOCK >CLK D -BIT LTCH OUT dder adds new value (DT) to accumulator Edge trigger prevents immediate feedback Output (OUT) may be shown with light bulbs Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

12 Number dder 11 CONTROL PNEL OSCILLTOR CLK RIPPLE O COUNTER 16 W DI 64Kx RM DO B -BIT DDER CO S CI Everything put together >CLK D -BIT LTCH OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

13 Halt 12 OSCILLTOR ND CLK RIPPLE O COUNTER NOT HLT Halt when external switch is turned on Or: cut connection to clock if ripple counter reaches final number Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

14 13 multiple operations Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

15 Modification: lternate dd and Subtract 14 Let s say we want to alternate between adding and subtracting We already built an integrated adder and subtractor B0 B1 B2 B3 SUB B0 B1 B2 B3 SUB CO 4-BIT FULL DDER S0 S1 S2 S3 CI SUB OVERFLOW SUM Idea: indicate operation from last bit of ripple counter Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

16 lternate dd and Subtract 15 CONTROL PNEL OSCILLTOR ND CLK RIPPLE O COUNTER O0 16 W DI 64Kx RM DO NOT HLT SUB CO LU S B CI Bit 0 of ripple counter as instruction flag >CLK D -BIT LTCH OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

17 16 instructions Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

18 Goal 17 Control operations by instructions stored in memory programmable computer First idea separate instruction memory instructions: add or subtract Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

19 16 Instruction Memory 1 CONTROL PNEL OSCILLTOR ND CLK O RIPPLE COUNTER Data NOT 16 W DI 64Kx RM DO HLT CONTROL UNIT W DI 64Kx RM DO SUB CO LU S B CI Code >CLK D -BIT LTCH CONTROL PNEL OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

20 Operation Codes for Instructions 19 Each operation is encoded by a byte value Operation dd Subtract Code (hex) 20h 21h Example ddress Code Data ccumulator 0000h 20h dd 01h 00h 01h 0001h 20h dd 02h 03h 0002h 21h Subtract 01h 02h 0003h 20h dd 0h 0ah 0004h 21h Subtract 03h 07h Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

21 More Instructions 20 Load: load number from memory into accumulator Store: store accumulator value in memory Halt: block clock Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

22 Operation Codes for Instructions 21 Each operation is encoded by a byte value Operation Load Store dd Subtract Halt Code (hex) 10h 11h 20h 21h FFh Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

23 16 More Wiring CONTROL PNEL 22 OSCILLTOR ND CLK O RIPPLE COUNTER Data NOT 16 W DI 64Kx RM DO HLT W DI HLT 64Kx RM CTRL UNIT INSTR DO STR SUB LD Code NOT SUB CO LU S SELECTOR B CI >CLK D -BIT LTCH CONTROL PNEL OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

24 16 Load CONTROL PNEL 23 OSCILLTOR ND CLK O RIPPLE COUNTER Data NOT 16 W DI 64Kx RM DO HLT W DI HLT 64Kx RM CTRL UNIT INSTR DO STR SUB LD Code NOT SUB CO LU S SELECTOR B CI >CLK D -BIT LTCH CONTROL PNEL OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

25 16 Store CONTROL PNEL 24 OSCILLTOR ND CLK O RIPPLE COUNTER Data NOT 16 W DI 64Kx RM DO HLT W DI HLT 64Kx RM CTRL UNIT INSTR DO STR SUB LD Code NOT SUB CO LU S SELECTOR B CI >CLK D -BIT LTCH CONTROL PNEL OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

26 16 Halt CONTROL PNEL 25 OSCILLTOR ND CLK O RIPPLE COUNTER Data NOT 16 W DI 64Kx RM DO HLT W DI HLT 64Kx RM CTRL UNIT INSTR DO STR SUB LD Code NOT SUB CO LU S SELECTOR B CI >CLK D -BIT LTCH CONTROL PNEL OUT Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

27 Operations and Wiring 26 Each operation changes certain flags Operation Code LD STR SUB HLT (hex) Load 10h Store 11h dd 20h Subtract 21h Halt FFh Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

28 Program Example 27 ddress Code Data ccumulator 0000h 10h Load 56h 00h 56h 0001h 20h dd 2h 0h 0002h 21h Subtract 3h 4h 0003h 11h Store 4h 0004h FFh Halt 4h Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

29 2 adding 16 bit numbers Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

30 dding 16 Bit Numbers 29 1 byte integers will not suffice in practice unsigned: 0 to 255 signed: -12 to 127 Let s use 2 bytes (16 bit) How can we do addition with our -bit adder? dd the bytes separately Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

31 Example 30 Task: 76Bh + 232Ch Lower order byte 0Bh +2Ch D7h Higher order byte 076h +23h h Putting it together: 99D7h Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

32 nother Example 31 Task: 76Bh + 236Ch Lower order byte 0Bh +6Ch h Higher order byte (add the carry) 001h +76h +23h h Putting it together: 9D7h Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

33 More Instructions 32 dd with Carry when addition results in a carry, store this in a flag new add instruction that includes carry if flag set Subtract with Borrow when subtraction results in a carry, store this in a flag new subtract instruction that includes carry if flag set Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

34 Circuit 33 HLT CTRL UNIT STR CO SUB INSTR CI LD SUB CO LU S B CI >CLK D Carry Flag Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

35 Instructions 34 Each operation is encoded by a byte value Operation Load Store dd Subtract dd with carry Subtract with borrow Halt Code (hex) 10h 11h 20h 21h 22h 23h FFh Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

36 Code 35 ddress Code Data Carry ccumulator 0000h 10h Load Bh 0001h 20h dd 6Ch 0002h 11h Store 0003h 10h Load 76h 0004h 22h dd with carry 23h 0005h 11h Store 0006h FFh Halt 0 00h 0 Bh 1 17h 1 17h 1 76h 0 9h 0 9h 0 9h Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

37 36 addressing memory Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

38 Motivation 37 Currently using two memories code memory for instructions data memory Very limiting Instead: store code and data in same memory add explicit addresses to instructions Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

39 dapted 16-Bit dder 3 Memory ddress 4000h 4001h 4002h 4003h Data Bh 76h 6Ch 23h Code Note: Instructions take up 1 or 3 bytes ddress Bytes Code 0000h 10h 00h 40h Load 4000h 0003h 20h 02h 40h dd 4002h 0006h 11h 04h 40h Store 4004h 0009h 10h 01h 40h Load 4001h 000Ch 22h 03h 40h dd with carry 4003h 000Fh 11h 05h 40h Store 4005h 0012h FFh Halt Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

40 Instruction Fetch 39 OSCILLTOR ND CLK O RIPPLE COUNTER NOT HLT W DI 64Kx RM DO CONTROL PNEL INSTRUCTION FETCH CLK INSTR X S >CLK D LTCH INSTR HLT CLK >CLK D LTCH Z D1 CTRL UNIT CI >CLK D LTCH D2 STR CO SUB LD 3 registers: code and 2 byte data Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

41 Instruction Fetch 40 OSCILLTOR ND CLK O RIPPLE COUNTER NOT HLT W DI 64Kx RM DO CONTROL PNEL INSTRUCTION FETCH CLK INSTR X S >CLK D LTCH INSTR HLT CLK >CLK D LTCH Z D1 CTRL UNIT CI >CLK D LTCH D2 STR CO SUB LD Transfer bytes from memory to instruction code and data register Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

42 Instruction Fetch 41 OSCILLTOR ND CLK O RIPPLE COUNTER NOT HLT W DI 64Kx RM DO CONTROL PNEL INSTRUCTION FETCH CLK INSTR X S >CLK D LTCH INSTR HLT CLK >CLK D LTCH Z D1 CTRL UNIT CI >CLK D LTCH D2 STR CO SUB LD Instruction fetch logic determines which register is written to Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

43 Instruction Fetch 42 OSCILLTOR ND CLK O RIPPLE COUNTER NOT HLT W DI 64Kx RM DO CONTROL PNEL INSTRUCTION FETCH CLK INSTR X S >CLK D LTCH INSTR HLT CLK >CLK D LTCH Z D1 CTRL UNIT CI >CLK D LTCH D2 STR CO SUB LD This is informed by instruction code Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

44 Instruction Fetch 43 OSCILLTOR ND CLK O RIPPLE COUNTER NOT HLT W DI 64Kx RM DO CONTROL PNEL INSTRUCTION FETCH CLK INSTR X S >CLK D LTCH INSTR HLT CLK >CLK D LTCH Z D1 CTRL UNIT CI >CLK D LTCH D2 STR CO SUB LD Once all registers are filled, execute instruction Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

45 Data Paths 44 Data needs to be transferred in various ways dress passed on to memory (overriding program counter) dd/subtract: read byte from memory, pass to LU Load: Store: read byte from memory, store in accumulator read byte from accumulator, store in memory No detailed wiring worked out here... Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

46 45 multiplication Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

47 Plan 46 Multiplication by repeated addition Pseudo-code load number1 into accumulator loop subtract 1 from number2 last if number2 = 0 add number1 to accumulator store accumulator in result Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

48 Needed 47 Jump set the ripple counter to specified value Zero flag detect that subtraction resulted in number 0 implemented as flag of the LU Jump if zero check if zero flag is set only then update ripple counter otherwise, do nothing Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

49 Zero Flag 4 HLT CTRL UNIT STR CO SUB Z INSTR CI LD SUB CO Z LU S B CI >CLK D Carry Flag >CLK D Zero Flag Flag when the LU operation results in 0 Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

50 Instructions 49 Operation Load Store dd Subtract dd with carry Subtract with borrow Jump Jump if zero Jump if carry Jump if not zero Jump if not carry Halt Code (hex) 10h 11h 20h 21h 22h 23h 30h 31h 32h 33h 34h FFh Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

51 Code ( Bit Version) 50 Memory Code ddress 4000h 4001h 4002h Data 0Bh 0Fh 01h ddress Bytes Code 0000h 10h 00h 40h Load 4000h ; load number1 0003h 11h 03h 40h Store 4003h ; save in result 0006h 10h 01h 40h Load 4001h ; load number2 0009h 21h 02h 40h Subtract 4002h ; subtract 1 000Bh 31h 1h 00h jump if zero to 001h ; jump to end if done 000Fh 10h 03h 40h load 4003h ; load result 0012h 20h 00h 40h add 4000h ; add number1 0015h 30h 03h 00h jump to 0003h ; loop 001h FFh halt ; quit Philipp Koehn Computer Systems Fundamental: Instructions 16 February 201

SCRAM Introduction. Philipp Koehn. 19 February 2018

SCRAM Introduction. Philipp Koehn. 19 February 2018 SCRAM Introduction Philipp Koehn 19 February 2018 This eek 1 Fully work through a computer circuit assembly code Simple but Complete Random Access Machine (SCRAM) every instruction is 8 bit 4 bit for op-code: