Lda Ldx Ldy Sta Stx Sty
addressing modes LDX and LDY each have five addressing modes while STX and STY have three, and STA has seven. Recall that addressing modes determine how the CPU locates data that is retrieved from memory or how it locates where data is to be stored. The large number of addressing modes provided by the 6502 processor is an advantage in machine language programming because it allows the programmer more options in writing code for a given task. In Boxes 18, 19, and 20 the STA, STX, and STY...
Atari-assembler Befehlssatz
4. Getting Started In Machine Language 6. Advanced Techniques ____ 229 Decimal Values for the 6502 Instructions __321
Memory Map
This memory map is arranged to give you an overview of the organization of Atari memory. We have given emphasis to the specific memory locations that are directly useful in terms of sound and graphics as explained in the text of this book. See the end of the memory map for sources of the complete memory allocations. Page zero is found at locations zero to 255 0- FF . These locations are accessed faster and easier by the machine. On page 0 locations 0 to 127 are observed for the OS, while...
Dex Dey Inx Iny
A complete listing of the number of cycles for all instructions can be found in more advanced books on 6502 programming. For a simple loop, the time calculation goes like this LDX 80 LDX immediate 2 cycles LOOP DEX DEX 80 times 160 cycles 402 cycles times 5.6 x 10-7 .225 milliseconds. This, of course, is only an estimate of the time taken up by the loop because the jump and return instructions take CPU time as will any other instruction involving the outer loop. Each of the machine language...
Atari Assembly Language Programmers Guide
Weber Systems, Inc. Chesterland, Ohio The authors have exercised due care in the preparation of this book and the programs contained in it. The authors and the publisher make no warranties either express or implied with regard to the information and programs contained in this book. In no event shall the authors or publisher be liable for incidental or consequential damages arising out of the furnishing, performance, or use of this book and or its programs. Atari 400 , Atari 800 . Atari 800XL ,...
List of Boxes
4 Program - Display List Dump _ 79 5 Program - Position Concepts _ 86 6 Program - Modified Graphics 8 _ 87 7A Program - Mode 4 Display List _ 92 7B Program - Antic Mode 4 with Rocket _ 93 8 Program - Antic Mode 14 Display List _ 96 10 Program - POKEing in Colors _103 11 Program - Two Methods of Displaying _105 13 Utility - BASIC Character Generator _110 14 Program - Redefined Character _113 15 Utility - Multicolored Character Generator ___116 16 Program - Light Bulb Player _129 18 Program -...
Irqst Skctl Skstat
R Read serial port status W Interrupt request enable R Interrupt request status W Serial port control R Reads serial port status Locations 53776 to 54015 are a repeat of locations 53760 to 53775. As of this writing these locations have no use. PI A 6520 Chip is located at addresses 54016 to 54271. These locations are used for control ports, controller jacks one through four and to process VINTER and VPRCED. R W data from controller jacks one and two R W data to from jacks three and four W R...
Info Bmo
box around inverse video ES Escape Key BS Back space Box 42B. The Yellow Submarine SUBS Listing BOX 42C Vertical Scrolling Routine The Yellow Submarine 205 COUNT keeps track of how far we ve scrolled 206 SCRLREG keeps track of value to put in VSCROL. CPY 120 BEQ END STY COUNT LDX SCRLREG INX CPX STX VSCROL STX SCRLREG LDA 6 STA TIMER RTS 164,205 First check to see if submarine 200 has scrolled to top of screen 192,120 Here, the value 120 limits 240,19 the scrolling 132.205 Save Y for next pass...