; "Fast Action Graphics" ; ---------------------- ; Using Foreground/Background Processing ; Author Not Stated, but probably by John Perkins (??) ; Published in "Arcadian" Vol 2, No. 10 (Sept 17. 1980) ; ; - The program has been disassembled using using DZ80 2.0 ; by Adam Trionfo on August 15, 2011. This program can ; be assembled using ZMac. ; - Most of these comments in this program are from the ; original article in the arcadian. ; ; This program runs on a Bally/Astrocade in the expansion RAM ; beginning at $6000. This program was originally meant to ; be entered into the Blue Ram Utility as a machine language ; program. This is still a method that works well to enter to program, ; thus the hexadedimal machine language code for the entire 119 byte ; program is given here: ; ; 0 1 2 3 4 5 6 7 8 9 A B C D E F ; $6000 - F3 D9 3E 60 ED 47 3E 18 D3 0D 21 6A 60 11 00 70 ; $6010 - 01 0D 00 ED B0 D9 FB C9 1A 60 CD B0 20 ED 73 7E ; $6020 - 70 31 7E 70 F5 C5 D5 E5 DD E5 FD E5 DB 1C 32 02 ; $6030 - 70 FF 00 07 4C 60 3F 00 70 52 60 07 4C 60 02 FD ; $6040 - E1 DD E1 E1 D1 C1 F1 ED 7B 7E 70 C9 1F 00 70 56 ; $6050 - 60 08 00 98 00 50 00 00 02 08 28 00 82 00 82 00 ; $6060 - A8 2A 80 80 80 A8 00 80 00 2A 20 80 00 05 00 00 ; $6070 - 00 03 05 00 00 00 03 ; ; Description: ; ------------ ; Fast Action Graphics are demonstrated in this machine code background ; routine. Enter this program using your Blue Ram Utility and watch ; the Perkin's Engineering graphic (a "PE") bounce around the screen ; without disturbing what is there! ; The speed of motion is controlled by the #1 knob. Another special ; effect produced by this routine is a "curtain of invisibility" at the ; top of the screen. As the graphic moves behind the curtain, it ; disappears one-half pixel at a time. The size of the curtain is also ; controlled by the #1 knob. Notice that you can still enter programs, ; etc. in BASIC because the graphic movement is performed in the ; background mode where it does not tie up the processor. ; ; To Stop the background process from the foreground process using BASIC, ; enter: :RETURN [GO]. To Start it up again, enter: CALL 24576 [GO] ; INCLUDE "HVGLIB.H" ; Home Video Game Library ORG $6000 ; First Byte of Blue Ram Expansion Memory DI ; Disable the Current Background Process ; Reassign background processing to a routine whose beginning address ; can be found in the word at location $6018. EXX LD A,$60 ; High Order Byte Address of Interrupt Vector LD I,A ; Load Interrupt Vector Register LD A,$18 ; Low Order Byte Address of Interrupt Vector OUT (INFBK),A ; Port $0D, Write INterrupt FeedBacK ; Move a 13-byte Motion Control Table (aka Vector Table) into ; the $7000 area so that this routine can operate in the ROM ; mode if desired. L600A: LD HL,L606A ; Source Address LD DE,$7000 ; Destination Address LD BC,$000D ; Load Counter with 13 LDIR ; Reanable the background processor EXX EI RET ; Return to the program program from which it was called L6018: DW L601A ; Points to Interrupt Routine ; Envoke the original Background Processor. This is necessary so ; that the note timer can be decremented as required when printing ; characters. Otherwise, the foreground program would hang up ; while waiting for the timer to clear and not be able to continue ; with the foreground program. ;L601A: CALL $20B0 ; Envoke the Bally BASIC original Background Processor L601A: CALL $21FD ; Call AstroBASIC's Interrupt Routine ("BG Processor") ; Save all the Z80 registers so that their original values can ; be returned to the foreground program. LD ($707E),SP ; Load the contents of SP to expansion RAM LD SP,$707E ; Move the Stack point to expansion RAM PUSH AF PUSH BC PUSH DE PUSH HL PUSH IX PUSH IY ; Read the #1 controller knob and place the value in the motion ; control table at the current motion velocity multiplier. IN A,(POT0) ; Pot $1C, Read POTentiometer 0 for player 1 knob LD ($7000+VBTIMB),A ; Place Knob Value into Time Base ; Invoke special graphics and animation services built into the Bally ; Arcade internal ROM. SYSTEM INTPC ; UPI INTerPret with Context ; DO MCALL ; UPI Macro CALL interpreter DW L604C ; Macro Address ; DO VECT ; UPI VECTor move coordinate DW $7000 ; Vector Block DW L6052 ; Limit Table (AKA Motion Control Table) ; DO MCALL ; UPI Macro CALL interpreter DW L604C ; Macro Address ; DONT XINTC ; UPI eXit INTerpreter with ; ; Restore the Z80 registers to their original values and return ; to the foreground program in progress. POP IY POP IX POP HL POP DE POP BC POP AF LD SP,($707E) ; Restore the contents of the SP RET ; Write Pattern to Screen ; This Macro is called from the ROM Interpreter using MCALL. L604C: DO VWRITR ; UPI Vector WRITe Relative DW $7000 ; Vector Block DW L6056 ; Pattern Address = 24662 DONT MRET ; Return from to ROM Interpreter ; Limite Table for VECT Routine - Define the boundaries of the ; graphic motion. (152 Pixels Wide and 40 High) L6052: DB 0 ; X Lower Limit DB 152 ; X Upper Limit DB 0 ; Y Lower Limit DB 80 ; Y Upper Limit ; Pattern Address ; Define the Corordinate Reference for the graphic (0,0) and ; the size of the graphic (8 x 8 pixels). L6056: DB 0,0 ; X,Y Displacement DB 2,8 ; Width and Height (2 Bytes x 8 bytes) ; The graphic data of the "PE" Image. Note that only the odd bits ; are used. This is very important when working with this BASIC ; since even bits store the actual program statements. If these ; even bits are disturbed, the BASIC program will be altered, ; usually catastrophically. L605A: DB 00101000B,00000000B ; . 2 2 . . . . . DB 10000010B,00000000B ; 2 . . 2 . . . . DB 10000010B,00000000B ; 2 . . 2 . . . . DB 10101000B,00101010B ; 2 2 2 . . 2 2 2 DB 10000000B,10000000B ; 2 . . . 2 . . . DB 10000000B,10101000B ; 2 . . . 2 2 2 . DB 00000000B,10000000B ; . . . . 2 . . . DB 00000000B,00101010B ; . . . . . 2 2 2 ; Vector Block (Accessed from $7000) ; Defines the constraints for the motion control table. ; These values define 5/256'ths of a pixel times the ; current velocity multiplier worth of motion in both ; the X and Y coordinates with each update (60 times ; per second). The fastest speed, therefore, is 5 pixels ; x 60 updates = 300 pixels per second. The "$03's" in ; the table indicate that the graphic is to bounce off the ; sides instead of stopping. L606A: DB $20 ; Magic Register (VBMR) DB $80 ; Vector Status (VBSTAT) DB $00 ; Time Base (VBTIMB) DB $05 ; Delta X Low (VBDXL) DB $00 ; Delta X High (VBDXH) DB $00 ; X Position Low (VBXL) DB $00 ; X Position High (VBXH) DB $03 ; X Checks Mask (VBXCHK) DB $05 ; Delta Y Low (VBDYL) DB $00 ; Delta Y High (VBDHL) DB $00 ; Y Position Low (VBYL) DB $00 ; Y Position High (VBYH) DB $03 ; Y Checks Mask (VBYCHK)