Java core programming, Lecture notes of Java Programming

Download Java core programming and more Lecture notes Java Programming in PDF only on Docsity! KEYBOARD INTERRUPTs 8086 03/08/2023 1 The Purpose of Interrupts Interrupts are particularly useful when interfacing I/O devices that provide or require data at relatively low data transfer rates . If the person using the keyboard typed one character per second. The software of the Processors waited an entire second between each key stroke for the person to type another key . This process was such a tremendous waste of time that designers developed another process, Interrupt processing to handle this situation. Interrupt processing allows the microprocessor to execute other software while the keyboard operator is thinking about what key to type next. 03/08/2023 2 INT Instruction The term type in the instruction format refers to a number between 0 and 255 which identifies the interrupt. When an 8086 executes an INT instruction. It will: 1. Decrement the stack pointer by 2 and push the flags onto the stack. 2. Decrement the stack pointer by 2 and push the contents of CS onto the stack. 3. Decrement the stack pointer by 2 and push the offset of the next instruction after the INT number instruction on the stack. 4. Get a new value for IP from an absolute memory address of 4 times the type specified in the instruction. For an INT 8 instruction. For example, the new IP will be read from address 00020H. 5. Get a new value for CS from an absolute memory address of 4 times the type specified in the instruction plus 2. For an INT 8 instruction, for example, the new value of CS will be read from address 00022H. 6. Reset both IF and TF. Other flags are not affected. 03/08/2023 5 INT 21h Instruction Hence in this section we are going to see about INT instructions used for Keyboard.(INT 21 h-DOS Interrupt) The int 21 h instructions are used to interrupt through the Keyboard, Files, Directives. Depending on the value that is moved to the ‘ah’ the operations will be done. The following slides will explain the different operations performed. 03/08/2023 6 INT 21h Instruction INT 21h / AH=1 - read character from standard input, with echo, result is stored in AL. if there is no character in the keyboard buffer, the function waits until any key is pressed. example: mov ah, 1 int 21h INT 21h / AH=2 - write character to standard output. entry: DL = character to write, after execution AL = DL. example: mov ah, 2 mov dl, 'a' int 21h 03/08/2023 7 Other INT 21h Instruction INT 21h / 6h;direct console input or output. INT 21h/0Bh; Get input Status INT 21h/0Ch; Flush keyboard buffer and read standard input INT 21h/0Eh; Select default drive INT 21h/19h; Get current default drive INT 21h/25h; Set interrupt vector INT 21h/35h; Get interrupt Vector INT 21h/39h; Make directory INT 21h/3Ah; Remove directory INT 21h/3Bh; Set current directory 03/08/2023 10 Other INT 21h instruction INT 21h/3Ch;create or truncate file INT 21h/3Dh;Open Existing file INT 21h/3Eh;Close file INT 21h/3Fh;Read from File INT 21h/40h;Write to file INT 21h/41h;Delete File INT 21h/42h;Set current File Position INT 21h/47h;Get current Directory INT 21h/4Ch;return control to the operating system(STOP PROGRAM) INT 21h/56h; rename file/move file   03/08/2023 11 Example Programs INPUT A CHARACTER AND PRINT THE CHARACTER IN THE OUTPUT .model small .stack 100h .code mov ax, @data mov ds, ax mov ah, 1h ; keyboard input subprogram int 21h ; read character into al mov dl, al ; copy character to dl mov ah, 2h ; character output subprogram int 21h ; display character in dl end 03/08/2023 12 INT 16h INSTRUCTION 03/08/2023 15 INT 16h is the basic BIOS keyboard operation used extensively by software developers and provides the following services according to a function code that you load in AH. INT 16h/03h: set typematic Repeat rate INT 16h/05h: Keyboard write.  INT 16h/10h: Read keyboard Character INT 16h/11h: Determine whether character is present or not INT 16h/12h: Return Keyboard Status. INT 10h Instructions INT 10h instruction is used for the video mode. Even this INT instruction has many operations that works according to the value moved onto the ‘ah’. Option 0H – Sets video mode. Registers used:  AH = 0H  AL = Video Mode. 03/08/2023 16 INT 10h Instructions 03/08/2023 17 The following are some of the services offered by INT 10 H. INT 10H/00H; set video mode INT 10H/01H; set cursor size INT 10H/02H; set cursor position INT 10H/03H; return cursor status INT 10H/05H; select active page INT 10H/06H; scroll up screen INT 10H/07H; scroll down screen INT 10H/0Ah; display character INT 10H/0CH; Write pixel dot INT 10H/13H; Return video information INT 10h Instructions 03/08/2023 20 INT 10h / AH = 13h - write string. input: AL = write mode:     bit 0: update cursor after writing;     bit 1: string contains attributes. BH = page number. BL = attribute if string contains only characters (bit 1 of AL is zero). CX = number of characters in string (attributes are not counted). DL,DH = column, row at which to start writing. ES:BP points to string to be printed. INT 10h Instructions 03/08/2023 21 example: mov al, 1 mov bh, 0 mov bl, 0011_1011b mov cx, msg1end - offset msg1 ; calculate message size. mov dl, 10 Mov dh, 7 push cs pop es mov bp, offset msg1 mov ah, 13h int 10h jmp msg1end msg1 db " hello, world! “ msg1end:   THANK YOU 03/08/2023 22