Machine Language Tutorial Disk

*************************************** * * * PART VI OF DR. FIRMWARE'S M.L. TUT. * * * *************************************** As was previously said, this article is about monitor, assemblers and other methods of entering M.L. programs into memory. Poking and calling. To enter a program into memory from BASIC, one can POKE the decimal equivalents of the hex op-codes (the values that the microprocessor understands) into the appropriate range of memory and then calling the subroutine with a 'CALL' statement. This method is quite tedious and complicated due to the fact that one would have to derive the hex codes by oneself by looking them...

*************************************** * * * M.L. PART FIVE BY DR. FIRMWARE * * * *************************************** This part is going to be about the arithmetic and logic unit of the 6502. The ALU is what does the addition and subtraction and bit operations. Presently, we will only cover the math, leaving the bit operations for later. If you read the previous column, you will have noticed that the CMP 'subtracts' two numbers. this subraction takes place in the ALU. To subtract two numbers, we use the SBC command. In immediate addressing mode, the arguement is subtracted from the value currently held in accumulator, and the result...

*************************************** * MACHINE LANGUAGE TUTORIAL PART IV * *************************************** The CMP command CMP stands for CoMPare accumulator. It has an immediate mode. In immediate mode, what happens is this: the value of the arguement is subtracted from the contents of the accumulator and this result is dicarded except for the effects on the zero, negative and carry flags. English translation immediately following. We'll take it slowly. The value of the arguement is the byte following the operator. This value is subtracted from the contents of the accumulator. Say the arguement is $40 and the accumulator hold...

*************************************** * * * PART VII - ASSEMBLERS * * WRITTEN BY DR. FIRMWARE * * * *************************************** Assemblers are used for easily writing up code from mnemonics to hex. To do this by hand is tedious, to say the least, and eventually one will make an error here or there. Mnemonics are the codes that we have been using, like 'LDA'. Since these do not signify the addressing mode, there is a set of symbols that are normally used. To indicate immediate addressing mode, we put a '#' in front of the arguement. To indicate absolute addressing mode, we just put the address. To indicate indexed absolute m...

*************************************** * * * * * MACHINE LANGUAGE TUTORIAL DISK * * * * WRITTEN BY DR. FIRMWARE * * * * * *************************************** PART II Machine language command structure. Even though this sounds complicated, the structure of machine language commands is quite simple. The command is one to three bytes long and consists of two sections, the operator and the arguement. The operator is always one byte long and the arguement is either zero, one or two bytes long. If the arguement is zero bytes long, then it is said that there is no arguement for that command. The accumulator The accumulator is the primary r...

*************************************** * * * * * MACHINE LANGUAGE TUTORIAL DISK * * * * WRITTEN BY DR. FIRMWARE * * * * * *************************************** The aim of this disk is for you the reader to understand machine language to an extent so that you can program fully in machine language (ml). PART I The fundamentals. The first part of the course is number bases. if you undestand binary and hexadecimal numbers and conversion between these and decimal, you can skip to the next section. Binary: Base two. Number bases are what we are dealing with here. The number base that we normally use in everday life is decimal. 'Decimal' com...