1. Assembler MCS51 - machine language

2. Structure of programme In general a single assembler programme line has following structure: for example: go_here:adda,r0 ;adding to accumulator number from R0 movr6,a ;send back result to R6 Assembler MCS51 2/16

3. where: - text field at least 1 char width, used to declare identifiers/labels which should be followed by colon and space (': '), separating label from the rest of the line - text field for the symbolic name of processor instruction; also used for placing so called directives Assembler MCS51 3/16

4. where - cont.: - optional text field, which contents depends on used in instruction name field instruction or directive here the list of instruction operands/directive description should be placed; - optional text field, which starts with semicolon (‘;’), intended for free text, explaining programmed operations; comment can start at any place in program line, especially from the first column (omitting other fields). Assembler MCS51 4/16

5. Label purpose: 1. Identifiers of the locations in processor address space, for identify: jump addresses, like: here: add A,P0 starting addresses of subroutine, like: acall dod3B ;add 3-byte numbers basic addresses of data structure, like: table1: db 12,234,0,11 ; table of 1-byte values Assembler MCS51 5/16

6. Label purpose : 2. Identifiers of the program constants, - making easier to use them; - increasing program readability, like: CR EQU 13 ;carriage return ASCII char 3. Identifiers of the program variables, by assigning to them their starting address in memory space, like using EQU directive: date EQU 70h ;variable for day of the month.... mov r1,#date ;R1<-variable ‘date’ address Assembler MCS51 6/16

7. Constants: Char or number values predefined during assembly process or read out from external sources during linking. Examples: constantmeaning binary representation ‘A’single ASCII char 41h ‘text’string of ASCII chars74h,65h,78h,74h 787, 787Ddecimal number0313h 10011Bbinary number13h 2AFhhex number02AFh 2A0Hhexadecimal number02A0h 0F00hhexadecimal number0F00h 0x2AF, $2AFhexadecimal number02AFh 0457octal number012Fh 457Q, 457q octal number 012Fh 457O, 457ooctal number 012Fh Identifier with predefined valueaccording to the value Assembler MCS51 7/16

8. Expressions usage: Exemplary, instead the declarations: var1 equ4500h var2 equ4502h var3 equ4504h var4 equ4508h we can write: var1 equ4500h var2 equvar1+2 var3 equvar2+2 var4 equvar3+4 Assembly result is the same, but the second notation makes corrections easier Assembler MCS51 - expressions 8/16

9. Possible operators: Assembler MCS51 – expressions 9/16

10. Dostępne funkcje wyrażeń: Operator precedence: - braces ( ); - NOT, HIGH, LOW; - +, - (as a sign of the operand); - *, /, MOD; - +, - ; - SHR, SHL; - AND, OR, XOR; -, >=, >, LT, LTE, EQ, NE, GTE, GT. Assembler MCS51 - expressions 10/16

11. Assembler MCS51 - directives 11/16

12. Assembler MCS51 – directives 12/16

13. Assembler MCS51 - directives 13/16

14. Assembler MCS51 - directives 14/16

15. Assembler MCS51 - directives 15/16 CSEG, DSEG, ISEG, BSEG, XSEG – define the memory space segment (CODE, internal RAM addressed directly or indirectly, directly addressed bits or external RAM) for the following objects (instructions, constants, data structures, labels, etc.). Possible usage form: xSEG – switching to selected memory spaces; if selected segment was already used, its addressing is continued, either addressing starts from 0000h xSEG AT address - switching to selected memory spaces with defining the start address

16. Assembler MCS51 - directives 16/16 Exemplary usage: bseg at10h;switching to directly addressed bits with start address ;equal to 10h (it matches with bit #0 of byte placed ;in internal data memory at location 22h) flag1:dbit1;reservation of single-bit variables at bit locations: flag2:dbit1;10h & 11h (22h.0 & 22h.1) cseg at200h;switching to program memory space at address 200h numbers:db23,33,51,92,99 ;5-byte table with program constants ;placed at addresses 200h..204h org0 ajmpini;begin of the program