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Consider the assembler directives given below when answering the following questions.
- Show the data in memory after the directives above have been assembled.
- Based on your answers above, show the value of each label in the symbol table after the first pass of the assembler.
- Based on your answers above, show the assembly code for each instruction below, as it appears after the second pass of the assembler.
3a. MOVE.W #INC, D
MOVE.W #1, D
3b. MOVE.L ARRAY, D
MOVE.L $002002, D
3c. MOVE.L #MAX, A
MOVE.L #$002000, A
CEG 320/520: Computer Organization and Assembly Language Programming
Fall, 2004 In Class : Assembler Directives and the Symbol Table - Solution updated:20-sep-
1 ORG $
2 MAX DC.W 5
3 INC EQU 1
4 ARRAY DS.L 2
Memory Address Contents (in hexadecimal) Label (if applicable) $002000 $00 05 MAX $002002 ???? ARRAY (1st long word) $002004 ????^ ARRAY (1st long word) $002006 ???? ARRAY (2nd long word) $002008 ???? ARRAY (2nd long word)
Label Value MAX $ INC 1 ARRAY $
- Based on your answers above, give the instructions that would perform the operation described in each question.
4a. Move the address of ARRAY into address register A0.
MOVE.L #ARRAY, A
4b. Move the value of MAX into data register D1.
MOVE.W MAX, D
4c. Move the value of INC into data register D1.
MOVE.W #INC, D
4d. Move the first element of ARRAY into data register D1.
MOVE.L ARRAY, D
- Describe the problem with each of the following instructions, and give the correct version.
5a. MOVE.W INC, D
After INC is replaced with the number 1 during the second pass, this instruction looks like the source operand is absolute long, but it is referencing memory at location $000001, which is probably not what you want (it could be, but it is unlikely). Correct: MOVE.W #INC,D
5b. MOVE.W #ARRAY,A
#ARRAY indicates that you would like to move the immediate value of the address of ARRAY into A0. However, you have indicated that the operand size is W (WORD). Addresses are 24 bits, longer than a WORD, and therefore you will have incomplete information in A0. Correct: MOVE.L #ARRAY,A
5c. MOVE.W ARRAY,D
The elements in ARRAY were declared to be LONG WORDS, so using just .W here would result in copying only a part of the first array element. Correct: MOVE.L ARRAY,D
