1. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 ME 4447/6405 Microprocessor Control of Manufacturing Systems and Introduction to Mechatronics Instructor: Professor Charles Ume Lecture #10

2. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405

3. ME4447/6405 ASCII Character Codes ASCII – American Standard Code for Information Interchange ASCII assigns a hexadecimal ‘code’ to individual characters Examples: CharacterASCII ‘A$41 ‘E$45 ‘e$65(Note: Different codes for lower and upper case) ‘1$31 BS$08(Note: BS is Backspace. ) A microcontroller must send these codes to a display terminal in order for the terminal to display these characters.

4. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 ASCII Character Codes (continued) Hex to ASCII Conversion table from Programming Reference Guide Page 58

5. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 ASCII Character Codes An array of characters is called a string Example: character arrayStringASCII Representation ‘H ‘e ‘l ‘l ‘o “Hello”$48 $65 $6C $6C $6F Note: CharacterASCII ‘H$48 ‘e$65 ‘l$6C ‘o$6F

6. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405

7. ME4447/6405 Assembly Directive Types Assembly Control ORG, END Symbol Definition EQU Data Definition/Storage Allocation FCC, FCB, FDB, RMB, ZMB, BSZ, FILL Listing Control PAGE, OPT

8. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 Assembly Control

9. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 ORG and END ORG : Stores translated machine language instructions in sequence starting at given address for any mnemonic instructions that follow END: Stop translating mnemonics instructions until another ORG is encountered (Note: These were already discussed in Lecture 7)

10. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 Symbol Definition

11. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 EQU EQU lets you refer to a number or an address as a variable name. Example: VALAEQU $10*LABEL VALA USED TO REFER TO $10 ORG $1000 LDAA #VALA*LOAD HEX NUMBER $10 IN ACCUMULATOR A LDAB VALA*LOAD CONTENT OF MEMORY LOCATION $10 *IN ACC. B SWI END Same As: VALAEQU $10*LABEL VALA USED TO REFER TO $10 ORG $1000 LDAA #$10*LOAD HEX NUMBER $10 IN ACCUMULATOR A LDAB $10*LOAD CONTENT OF MEMORY *LOCATION $10 IN ACC. B SWI END

12. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 Data Definition/Storage Allocation

13. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 FCC FCC – Form Constant Character string FCC stores ASCII characters into consecutive bytes of memory. Any printable ASCII characters can be contained in the string. String is specified between two identical delimiters, which can be any printable ASCII character. First non-blank character after the string is used as a delimiter.

14. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 FCC Cont’d $0400 $0401 $0402 $0403 $0404 Address PrebyteOpcode Operand 31 32 33 34 35 Example: ORG $0400 FCC “12345” Result

15. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 FCB FCB – Form Constant Byte FCB has one or more operands. Value of each operand is truncated to eight bits, and is stored in single byte of object program. Operand may be a numeric constant, character constant, a symbol or an expression. Multiple operands are separated by commas, and are stored in successive memory bytes.

16. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 FCB Cont’d Example: VALA EQU $10 ORG $0400 FCB $34,’A, $28AC, $0A,VALA $0400 $0401 $0402 $0403 Address PrebyteOpcode Operand 34 41 AC 0A Result $040410

17. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 FDB FDB – Form Constant Double Byte FDB stores a double (two byte) word. May have one or more operands separated by commas. Operand may be a numeric constant, a character constant, a symbol, or an expression.

18. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 FDB Cont’d Example: ORG $0400 FDB $1234,’&,’G Note: ASCII value for & is $26 ASCII value for G is $47 $0400 $0401 $0402 $0403 $0404 Address PrebyteOpcode Operand 12 34 00 26 00 47 $0405 Result

19. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 RMB RMB – Reserve Memory Byte RMB saves a place in memory for a number. Example: ORG $0400 XVAR RMB 2 *TWO MEMORY *LOCATIONS $0400 *and $0401 ARE *RESERVED FOR XVAR ORG $1000 LDD #$FFAA STD XVAR SWI END $0400 $0401 Address PrebyteOpcode Operand FF AA Result

20. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 Question a student asked: What happens if you change the previous example to "XVAR RMB 3" instead of "XVAR RMB 2" ? What happens to the 3rd reserved byte when a 2 byte number is stored in XVAR? Modified Program: ORG $0400 XVARRMB 3 ORG $1000 LDD #$FFAA STD XVAR SWI END Answer: Remains unchanged

21. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 ZMB, BSZ ZMB – Zero Memory Byte and BSZ – Block Storage of Zero These directives fill a given number of memory locations with zero. Causes assembler to allocate a block of memory bytes, and each memory byte is assigned a value of zero. Both directives do the same thing. Number of bytes allocated is given in the operand field. Example: ORG $0400 ZMB #$02 BSZ #$02 $0400 $0401 Address PrebyteOpcode Operand 00 $0402 $0403 00 Result

22. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 FILL Fill given number of memory locations with any number. (Note: Fill uses one byte. If two bytes are specified, then it will truncate it and use LS Byte.) Example: ORG $0400 FILL #$FF, #$02 $0400 $0401 Address PrebyteOpcode Operand FF Result

23. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 Question a student asked: What happens when the previous example is changed to "FILL #$9ABC, #$02" instead of "FILL #$FF,#$02"? What happens if you fill memory with a 2 byte number? Answer: FILL will just use the LS Byte Modified Example: ORG $0400 FILL #$9ABC,#$02 END (Note: There is no ”go 1000” on the screen since these are just assembly directives and not a program)

24. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 Listing Control

25. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 PAGE The PAGE directive causes a page break in the list file. If no source listing is being produced, the PAGE directive will have no effect. The directive is not printed on the source listing.

26. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 OPT Allows for various options in assembly of a program, including generating a listing and counting instruction cycles. Options: nol-no output listing (default) l-do an output listing noc-no cycle number count (default) c-turn on cycle count using zero initial value contc-turn cycle count on, begin with last value cre-create a cross reference table (default anyway) RMB s-create a symbol table (default anyway) EQU Example: OPT l – Print source listing from this point

27. George W. Woodruff School of Mechanical Engineering, Georgia Tech ME4447/6405 QUESTIONS???