Table of Contents. Why machine language? A look into the Amiga's memory. Bits, bytes, and words.
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Table of Contents. Why machine language? A look into the Amiga's memory. Bits, bytes, and words. Number systems. Inside the Amiga. Components and libraries. The MC processor. Addressing memory. Operating modes. User and supervisor modes.
Condition codes. The Instructions. The Development Assember. Our First Programs. Adding tables. Sorting a table. Converting numbering systems. Hardware Registers. Checking for special keys. Reading the mouse or joystick.
Tone production. Hardware registers overview. The Amiga. Operating System. Calling functions. Program initialization. Reserve memory. Before you tackle machine language, you should take a closer look at several things that are vital to machine language programming. Machine language is actually the only language the MC processor understands.
This process can take place either when the program is executed the BASIC interpreter , or before program execution the Pascal and C compilers. The great advantage of machine language over an interpreted and compiled program is machine language programs are faster.
With an interpreter like BASIC, each line must first be interpreted before it is executed, which requires a great deal of time. A Pascal or C compiler translates the source code into machine language.
This translation procedure does not produce programs that are as fast as a pure machine language program. Another advantage machine language has over BASIC is that an inter- preter is not needed for the execution of a machine language program.
Machine language can access all the capabilities of the computer since it is the language native to the computer. It is possible that machine language subroutines are required by a higher level language to access functions that aren't directly accessible by that language.
Before a machine language program can be written, you must know exactly what the program is required to do. You must also be aware of what resources are needed and available to achieve those goals. The most important of these resources is the memory in the Amiga.
Random Access Memory, referred to as RAM, allows information to be placed in it and then withdrawn at a later time. This memory consists of electronic components that retain data only while the computer is turned on or until a power-failure.
So that the computer is able to do something when it is first turned on, such as prompting for the WorkBench or Kickstart disk, a program has to remain in memory when the power is off. A memory type which can retain data without power is needed. This second memory type is known as ROM.
ROM stands for Read Only Memory, indicating that data can only be read from this memory, not written to it. This special type of ROM can actually be programmed once. Since it cannot be erased once programmed, it isn't encountered very of- ten. These special chips, which can be erased with ultraviolet light, have a little window on the surface of the chip usually covered by tape.
These chips function like RAM, except that information is not lost when the power is turned off. With the birth of the Amiga, another type of memory, WOM, was created. This particular type of memory is Write Once Memory. The Kickstart disk is read into this memory when the computer is first booted.
After this, no more data can be read into that memory. Actually this isn't a completely new component, but simply RAM that is locked once data has been read into it, after which the data can only be read from that memory. This memory is connected to.
Thus it is com- monly referred to as the hardware register, since the computer's hardware. We'll go into greater detail on how to use. Let's take a closer look at the structure and use of the memory most familiar to us all, RAM. The standard size in which memory is measured is a kilobyte Kbyte. One kilobyte consists of bytes, not as you might expect.
This unusual system stems from the computer's binary mode of operation, where numbers are given as powers of 2, including kilobytes.
To access a memory block of one kilobyte, the processor requires 10 connections which carry either one volt or zero volts. A byte. The individual numerical values that make up a byte, which also are the smallest and most basic unit encountered in any com- puter, are called bits short for binary coded digit. It may seem unimaginable, but a memory of that size.
Well, did you get 50? That's the right answer. The most simple method to arrive at this result is to simply add up the values of the digits that contained a 1.
The values of the first eight digits are as follows:. The octal system, whose base is eight, is similar. The character set consists of the numbers 0 to 7. The decimal equivalent of the octal num-. However, the important as the next one. The base number of the hexadecimal system is 16, and its character set ranges from 0 to F. Thus, A would be the equivalent of a decimal 10, and. F would be The binary and hexadecimal systems are the most important numerical sys- tems for assembly language programming.
It is quite easy to convert binary numbers into hexadecimal: simply split. Each of these groups of four digits then corresponds to one hexadecimal digit. Here's an example:. The opposite operation is just as easy. This method can also be used to convert binary into octal and vice versa, except that groups of three digits are used in that case. This binary number can then be converted into hexadecimal, as well:. In order to program machine language, it is not sufficient to know only the commands of the particular processor, one must also have extensive knowledge of the computer being programmed.
Let's take a good look inside the Amiga. The Amiga is a very capable machine, due to the fact that there are components that do a large part of the workload, freeing up the processor.
These are referred to as the "custom" chips, which perform various tasks independently of the processor. Custom chips This task force is comprised of three chips, whose poetic names are Agnus, Denise and Paula. The main task of Agnus, alias blitter, is the shifting of memory blocks, which is helpful for operations such as quick screen changes. Denise is responsible for transferring the computer's thoughts onto the screen.
To simplify the otherwise rather complicated procedure of utilizing these chips, several programs have been included in the Kick- start and Workbench libraries. These programs can be called by simple routines and then take over the operation of the respective chips.
If only these library functions are used to program the Amiga, the para- meters are the same, regardless of the language used. Only the parameter notation differs from language to language.
BASIC is an exception in this respect, since its interpreter translates the program calls, which is why you don't need to know how the Amiga executes these functions in order to use them.
The library functions are written in machine language and are thus closely related with your own machine language programs. Actually you could do without the library programs and write all of the functions yourself.
Amiga Machine Language 1991 Abacus
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Amiga machine language
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Amiga Machine Language