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Ремонт частотных преобразователей AVR Assembler Source Blog: LED_blink_Hello_World

Saturday, October 5, 2013


ремонт частотного преобразователя
                              ; Test 1: Learn to know parts of the board hardware output to the LEDs.
                              ; What to learn here:
                              ; - to access a output-port (Port B and the LEDs)
                              ; - the different parts of a typical assembler program
                              ; General conventions used here:
                              ; - Words in uppercase letters are command words of the assembler language
                              ;   or predefined ports of the processor.
                              ; - I define Words in lowercaseletters.
                              ; Assembler directive: define the target chip type
                              ; Usually you do not have to include the def.inc-file. But my installation
                              ; does not find the definition files in the proper subdirectory. So I include
                              ; it manually by adding these lines to my source code. Failure to include
                              ; these definitions would result in a number of error messages. Simply
                              ; copy the def.inc-file to the same directory where your source code resides
                              ; or add your whole path to the include-statement below.
.INCLUDE "8515def.inc"
                              ; The directives NOLIST and LIST switch off the listing of the INCLUDE-file
                              ; (the listing will be found in the file TEST1.LST).
                              ; Define register
                              ; This register is defined for the purpose of interim storage of values.
                              ; The .DEF statement renames one of the 32 8-bit registers to a easier
                              ; to remember name (here: mp). It is easier to use than its real name
                              ; R16. Renaming these register also has the advantage that whenever you
                              ; want to change such a location you'll just have to change the .DEF
                              ; statement. Otherwise you would have to go through all commands re-
                              ; ferencing the register R16 and change all these lines.
.DEF mp=R16
                              ; Restart
                              ; Up till now not one byte of code was created. Here we start with the
                              ; first code, we define the program start adress. Later we will see, that
                              ; this jump command at adress 0 is useful. Here the first byte of code is
                              ; created.
                              ; Whenever the AVR is restarted it starts its program execution at adress
                              ; 0000. Such a restart may be activated by a power-on, by a hardware
                              ; reset on the respective pin or by a watchdog-timer reaching its zero
                              ; count. (The watchdog timer is not used here.)
                              ; In all these cases a jump to a program called "main" will be executed.
                              ; RJMP means "Relative Jump". In a relative jump a relative distance
                              ; is added to the current execution adress and the program is executed
                              ; at this new adress. We don't have to care about this distance by now
                              ; because the assembler calculates this relative distance from the information
                              ; in our source code and adds it automatically - as long as the maximum
                              ; permissible distance of 2 kB for- or backwards is not exceeded, otherwise
                              ; the assembler stops with an error message.
 rjmp main
                              ; Here we start with our main program code. First we have to define a
                              ; label, because the assembler has to know that this is the target of a
                              ; jump. A label is a freely defined name, followed by ":". For a better
                              ; overview labels start in column 1 of a line, all commands start with a
                              ; blank or a tab character. Behind the label there could be a command,
                              ; but this is not used here.
                              ; First we need to define port B as output, because the LEDs are connected
                              ; to these port pins. This is done by writing eight ones to the data direction
                              ; register of port B. The data direction register of port B is named DDRB,
                              ; we don't have to care about its real adress, as the .def-file holds this
                              ; information already. We do that in two steps. First we load binary 1111.1111
                              ; to a register:
       ldi mp,0b11111111
                              ; The command LDI (LoaD Immediate) loads an 8-bit value into the register
                              ; mp. This command is only valid for the registers R16 to R31. That is why we
                              ; defined mp that way at the beginning of this source code file. Commands
                              ; with two parameters are generally defined such that the first parameter
                              ; is the target (here: register mp), where the result of the operation goes to.
                              ; The second parameter is the value or location where the result comes from.
                              ; After execution of this command the register mp has the value 1111.1111
                              ; binary, FF hex or 255 decimal.
                              ; The 0b... of the beginning of the number is always a binary, 0x... is a hex
                              ; notation. The leading zero is the signal for the assembler to expect a number,
                              ; not a register or something else. Numbers without 0b... or 0x.. are decimal
                              ; by default. (LDI mp,255 would have the same result.)
                              ; This value has to be brought to the data direction register of port B now
                              ; to make all port pins to outputs. A 1 in the data direction register brings
                              ; the pin to switch on its output drivers, a zero makes it an input.
       out DDRB,mp
                              ; The command OUT writes register values (here: mp or R16) to a port
                              ; (here DDRB). DDRB is defined in the file "8515def.inc", which is already
                              ; read by the assembler when the .DEVICE-command or the .INCLUDE-
                              ; command above has been processed. So we don't need to care here
                              ; for the real adress of this port.
                              ; The following part of the program now writes zeros and ones to the port.
                              ; The LEDs are switched on and off with a high frequency. Because this
                              ; part of the program is repeated over and over again, I called it loop.
                              ; The label loop is jumped to whenver the processing of writing ones and
                              ; zeros is ended.
       ldi mp,0x00
       out PORTB,mp
                              ; LDI load eight zero bits to the universial register mp. OUT copies these
                              ; zeros to the port B. This time they are written to the port's output register
                              ; named PORTB.
                              ; The zeros set the LEDs on, because they are connected to the supply
                              ; voltage over resistors of 1 k (0=on, 1=off).
       ldi mp,0xFF
       out PORTB,mp
                              ; After that eight ones are loaded into the register mp and copied to
                              ; the same data port. That switches the LEDs off.
       rjmp loop
                              ; With this relative jump we jump back to the start of the loop and the
                              ; loop is repeated as long as power is supplied.
                              ; At 4 MHz xtal frequency every LDI- and OUT-command execution requires
                              ; 250 ns, the RJMP need 2 cycles and 500 ns. Every 1,500 ns the loop is
                              ; executed once, so with these values the LEDs are switched at 667 kHz.
                              ; After assembling this sourcefile the program will have eight words.
                              ; The file TEST1.LST holds the result of the assembling process in form
                              ; of a listing.
                              ; This was the first lecture, wait for more ...

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