Tutorial Lab 1 S2010

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E&CE 222

Lab Tutorial 1Hand Assembling

Prepared by: Peter Tysowski, T.A.E-mail: [email protected]

May 18, 2010

Spring 2010 term

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Lab 1 Tutorial Outline

Objectives of Lab 1 Program Operation and Loading Explanation of I/O Subroutines Modifying the Code Hand Assembling Operation Post Lab Subroutines Deliverables and Marking Scheme

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Objectives of Lab 1

Familiarize yourself with hand assembly ofMotorola 68000 instructions (ISA_A)

Familiarize with simple instructionse.g. and, bsr, cmp, jmp, jsr, lea, move, rts, suba, trap

Use different Effective Addressing modesAbsolute, Immediate, Register Direct, Register Indirect

Perform offset calculationse.g. beq, bne, bra

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Objectives of Lab 1

Use common assembler directives e.g. equ, org, dc

Handle monitor operationsTrap #15 vectors

Familiarize with input/output operations

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Program Operation

Print message asking for inputCall Read String subroutine

Read input characters into bufferAllocate a second bufferReverse the string into the second buffer

Call Output String subroutineExit to the Monitor

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I/O Subroutines

Out-CharacterStore parameter D0 on the stackOutput the register D1 (in ASCII)

Restore D0 from the stack

In-CharacterStore parameter D0 on the stack

Capture the input into D1 (in ASCII)Select the first byteDisplay the characterRestore D0 from the stack 6


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Modify the Program

lea BUFFER,A1 ;point to start of bufferbsr.w in_string ;read string andbsr.w out_crlf ;go to next line

* Scan for end of string.

move.l #BUFFER,A0 ;point to start of buffer

bloop1 tst.b (A0)+ ;see if we found the NULL yet.

bne bloop1 ;nope, keep loopingsuba.l #1,A0 ;ignore the NULL

movea.l #BUFFER+1024,A2 ;set up another buffer for result

Insert the necessary instructionshere - approximately 5 lines.

bsr.w out_string ;print the stringbsr.w out_crlf ;and go to new line

* Exitmove.l #$0000,d0TRAP #15

end ;optional, marking end of assembly

Handassemble

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Program Operation

Reverse string orderDetermines end of the stringDefines new bufferStores the reversed string in new bufferDisplays the reversed string

Buffer

Buffer + 1024

L

A

B

1

NULL

1

B

A1

A0

A2

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Program Loading

Using Motorola S-record FormatProduced by assemblers and compilers

Encapsulates opcodes with addresses and checksums

Using Text File (for Lab 1)Load the program through the terminal using text files

(OPCODES.txt)

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OPCODES.TXT

mm 10210000546869732070726f6772616d2077

696c6c207072696e74206f7574206120737472696e6720696e2074686520

etc

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Hand Assembling of Move

Move.L #100,D2 0 0 1 0 0 1 0 0 0 0 1 1 1 1 0 0

Size Field 00 Byte Operation 01 Word Operation 10 Long Word Operation 11 Reserved

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Hand Assembling (Move)

Translate: Move.L #100,D2

0010 0100 0011 1100 0000 0064 2 4 3 C 0000 0064Enter code:

mm.w10200000

243c064 12


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During Your Lab

Download the codes to the board Manually add on the rest of the program

Enter your hand-assembled program(including the new instructions required to complete it)

Run the program Debugging techniques: breakpoint, trace, disassemble

Test the program Print out the reverse of the input string

Finish assembly and test before demo day13


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Post Lab Subroutines

DEC2BINConverts a decimal ASCII string to a binary numberReads null-terminated string from A1 (doesnt modify A1)Converts ASCII bytes to decimal using Horners equation

Decimal: 3210 = (((3) * 10 + 2) * 10 + 1) * 10 + 0Store result in D1Write as subroutine (save registers to stack, use rts)Hint: use a loop, multiply instruction, and accumulatorHint: use data registers to hold temporary valuesNo error checking on input required 14


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BIN2DECConverts binary number to decimal ASCII stringReads word-sized binary number from D1 (doesnt modify it)Writes null-terminated string at location in A2Horners equation requires a divide subroutine

Hex: 3210 = (((3) * A + 2) * A + 1) * A + 0Size is 16-bit positive number (one word)No error checking on input requiredHint: use division and remainder instructions in loop 1Hint: output the decimal string then reverse it in loop 2 15


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Decimal ASCII String Binary Number(stored in Big Endian)

6980 0x36

0x39

0x38

0x30

0x1B44

or0 to 65535

16 bit positive number ranges from 0x0000 to 0xFFFF

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Deliverables

The Grade FormAccess from ACE and print it for the lab

Code for string-reverse program Full machine code listing (original program + additions) Lines added in assembly code, with comments

Post-lab: DEC2BIN and BIN2DEC subroutines In assembly language, with comments No hand assembly required

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Marking Scheme

LAB demo3 marks Lab completion (program must work 100%)2 marks Questions answered during lab demo

Individual mark May be asked about the program and/or asked to hand assemble

Post lab2 marks per subroutine (DEC2BIN & BIN2DEC)

Final Reports due 48 hours after demo, on ACE20% late penalty per day

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Marking Scheme

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Tutorial Lab 1 S2010

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