;;==========================================================================;; ;; Joe Zbiciak's Space Patrol for Intellivision. ;; ;; Main ISR, Main loop, task functions, initialization, etc. ;; ;; Copyright 2007, Joe Zbiciak, intvnut AT gmail.com. ;; ;; http://spatula-city.org/~im14u2c/intv/ ;; ;;==========================================================================;; ;;==========================================================================;; ;; TITLE / START ;; ;; ;; ;; This contains the title string and the startup code. We pre-empt the ;; ;; EXEC's initialization sequence by setting the "Special Copyright" bit ;; ;; in location $500C. This causes the code at 'START' to run before the ;; ;; built-in title screen is completely displayed. ;; ;; ;; ;; The Startup code does very little. Mainly, it sets the Interrupt ;; ;; Service Routine vector to point to our _real_ initialization routine, ;; ;; INIT. This is done because we can only get to GRAM and STIC registers ;; ;; during the vertical retrace, and vertical retrace is signaled by an ;; ;; interrupt. (Actually, we can have access to GRAM/STIC for longer ;; ;; if we don't hit the STIC 'handshake' at location $20, but then the ;; ;; display blanks. During INIT, the display does blank briefly.) ;; ;;==========================================================================;; TITLE: BYTE 107, "Space Patrol Teaser Edition", 0 ; Intercept/preempt EXEC initialization and just do our own. ; We call no EXEC routines in this game. START: PROC @@pass: MVII #STACK, R6 ;; ---------------------------------------------------------------- ;; ;; Initialize memory ;; ;; ---------------------------------------------------------------- ;; CALL FILLZERO.lp DECLE STACK-$2F0, $2F0 ; $2F0...$STACK. ;; ---------------------------------------------------------------- ;; ;; Game initialization. ;; ;; ---------------------------------------------------------------- ;; SETISR INITISR JSRE R5, CLRSCR DECR PC ENDP ;;==========================================================================;; ;; INIT ;; ;; Initializes the ISR, etc. Gets everything ready to run. ;; ;; This is called via the ISR dispatcher, so it's safe to bang GRAM from ;; ;; here, too. ;; ;; ;; ;; -- Zero out memory to get started ;; ;; -- Set up variables that need to be set up here and there ;; ;; -- Set up GRAM image ;; ;; -- Drop into the main game state-machine. ;; ;;==========================================================================;; INITISR PROC DIS MVII #$38, R2 MVO R2, $1F8 ;@@1: DIS MVII #STACK, R6 ; Reset the stack pointer CALL FILLZERO.lp DECLE $40 ; $00...$3F. (The STIC) DECLE 0 ; Prepare to zero all system RAM, PSG0,& STIC. MVI COLSTK, R1 ; Force display to color-stack mode SETISR MISCISR ; Point ISR vector to our ISR ; Ok, everything's ready to roll now. ; Load up our initial font and drop into the game loop JSRE R5, LOADFONT DECLE FONT B GAMELOOP ENDP ;;==========================================================================;; ;; LOADFONT -- Load a compressed FONT into GRAM. ;; ;; ;; ;; Font data is broken up into spans of characters that are copied ;; ;; into GRAM. Each span is defined as follows. ;; ;; ;; ;; Span Header: 2 numbers in 1 DECLE ;; ;; bit 6..0, bit 15: Skip Length (in bytes of GRAM memory) ;; ;; bit 14..7: Span Length (in bytes of GRAM memory) ;; ;; Span Data -- Span Length / 2 words ;; ;; ;; ;; Span data is encoded with two bytes in each 16-bit word. The lower ;; ;; byte is stored to the lower address, and the upper byte to the next ;; ;; address after it. ;; ;; ;; ;; The font is terminated with a span of length 0. ;; ;; ;; ;; INPUTS: ;; ;; R5 -- Points to word (1 decle in 16-bit ROM) containing ptr to font ;; ;; info. Code returns after this word. ;; ;; ;; ;; OUTPUTS: ;; ;; R0, R1, R4, R5 trashed. ;; ;; GRAM is updated according to the font specification. ;; ;; ;; ;;==========================================================================;; LOADFONT PROC MVI@ R5, R2 ; get font pointer @@1 PSHR R5 MVII #$100, R4 SDBD MVI@ R4, R1 SETISR @@isr DECR PC ; let ISR take over. @@isr: DIS SUBI #8, R6 MVO R1, $100 ; \ SWAP R1 ; |- restore old ISR MVO R1, $101 ; / MOVR R2, R5 ; get font pointer MVII #GRAM, R4 ; Point R4 at GRAM @@gramloop: MVI@ R5, R0 ; Get skip & span len. (in GRAM bytes) TSTR R0 ; Quit if skip/span == 0. BEQ @@gramdone MOVR R0, R1 ANDI #$7F8, R0 ; Extract span length. XORR R0, R1 ; Clear away span bits from word SWAP R1 ; Extrack skip value. ADDR R1, R4 ; Skip our output pointer. SLR R0, 1 ; Divide count by 2. @@charloop: MVI@ R5, R1 ; Get two bytes MVO@ R1, R4 ; Put the first byte SWAP R1 ; Put the other byte into position MVO@ R1, R4 ; Put the second byte DECR R0 ; Sheesh, do I have to spell this out? BNEQ @@charloop ; inner loop B @@gramloop ; outer loop @@gramdone: EIS PULR PC ENDP UPSND PROC PSHR R5 ;; ---------------------------------------------------------------- ;; ;; Update sound streams. All sound streams update at 60Hz. ;; ;; ---------------------------------------------------------------- ;; ; Update music CALL PLAY_SONG ; Arnauld's tracker ; Play any queued sound effects from running the engine2 MVI SFXQ, R1 TSTR R1 BEQ @@nosfx CLRR R0 MVO R0, SFXQ CALL DOPLAYSFX @@nosfx: ; Update sfx CALL UPSFX ; Update the sound stream PULR PC ENDP ;;==========================================================================;; ;; MISCISR ;; ;; This is the main interrupt service routine. It has to perform the ;; ;; following tasks: ;; ;; ;; ;; -- Run any miscellaneous "pre-VBLANK" task requested by main program. ;; ;; -- Hit the vertical blank handshake to keep screen enabled. ;; ;; -- Update any active sound streams. ;; ;; -- Drain and pixels queued up in the Pixel Queue. ;; ;; -- Count down task timers and schedule tasks when timers expire. ;; ;; -- Count down the 'busy-wait' timer if it is set. ;; ;; -- Detect a "Pause" request and pause the game if needed. ;; ;; ;; ;; Our code does not rely on any EXEC routines at all, except the ISR ;; ;; dispatch routine which saves and restores all the registers. (On a ;; ;; real Intellivision, we have no choice. On an emulator, that routine ;; ;; can be replaced with a separate non-EXEC routine which performs a ;; ;; similar dispatch, if we want to distribute this program without an ;; ;; EXEC ROM image but with an emulator.) ;; ;; ;; ;;==========================================================================;; BISTISR MVI TMP, R0 MVO R0, $28 MVO R0, $2C MISCISR PROC MVO R0, $20 @@1: @@wtimer: ;; ---------------------------------------------------------------- ;; ;; Count down the wait-timer, if there is one. ;; ;; ---------------------------------------------------------------- ;; MVI WTIMER, R5 DECR R5 BMI @@expired MVO R5, WTIMER @@expired: ;; ---------------------------------------------------------------- ;; ;; Other misc periodic stuff. ;; ;; ---------------------------------------------------------------- ;; MVI TICK, R0 ; Increment global tick counter INCR R0 MVO R0, TICK B ISRRET ENDP ;;==========================================================================;; ;; WAIT ;; ;; Busy-waits for the number of ticks specified after call, or in R0. ;; ;; ;; ;; INPUTS: ;; ;; R0 -- Number of ticks to wait (WAIT.1) ;; ;; R5 -- Return address ;; ;; ;; ;; OUTPUTS: ;; ;; R0 -- cleared ;; ;;==========================================================================;; WAIT1 MVII #1, R0 INCR PC WAIT PROC MVI@ R5, R0 @@1 MVO R0, WTIMER CLRR R0 @@loop: CMP WTIMER, R0 BNEQ @@loop JR R5 ENDP __ ;* ======================================================================== *; ;* This program is free software; you can redistribute it and/or modify *; ;* it under the terms of the GNU General Public License as published by *; ;* the Free Software Foundation; either version 2 of the License, or *; ;* (at your option) any later version. *; ;* *; ;* This program is distributed in the hope that it will be useful, *; ;* but WITHOUT ANY WARRANTY; without even the implied warranty of *; ;* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *; ;* General Public License for more details. *; ;* *; ;* You should have received a copy of the GNU General Public License *; ;* along with this program; if not, write to the Free Software *; ;* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. *; ;* ======================================================================== *; ;* Copyright (c) 2007, Joseph Zbiciak *; ;* ======================================================================== *; _