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Topic: Vertical blank interrupt

	Atari Graphics and Arcade Game Design-Chapter 6
		These interrupts are a powerful aid to the game programmer, who can use them to smooth animation, to enable players to be re-used in the bottom portion of the frame, to allow character sets and color registers to be changed mid-screen, and of course much more.
		This type of interrupt is sometimes called a "Raster Interrupt." Remember that the interrupt does not stop the TV raster process but causes the 6502 to execute a series of instructions at this specific time.
		When an interrupt occurs, the computer is sent to a vector in the operating system, which in turn sends it to a routine to determine what type of interrupt has occurred.
	www.atariarchives.org /agagd/chapter6.php (4338 words)

	Homebrew Nintendo DS Development Part 3
		Just like there is an interrupt for the Vertical Blank period, there is an interrupt for key events.
		We can have an interrupt function called immediately when a key is pressed.
		The interrupts tutorial demonstrates how to do this and outlines some disadvantages with the interrupt method.
	www.double.co.nz /nintendo_ds/nds_develop3.html (914 words)

	Systems Guide: Interrupts
		Recall from my discussion of raster scan graphics, that the term vertical blank is given to that time period when the electron beam is turned off and returned to the upper-left corner of the video screen, ready to start tracing a new frame.
		The vertical blank interrupt is an essential part of the ATARI Operating System and appears as a non-maskable interrupt (NMI) to the system.
		A vertical blank can be processed during a call to this routine.
	www.atarimagazines.com /vbook/interrupts.html (1135 words)

	Hardware Hacking » Programmable Video Sync Generator
		The ‘ACT715/LM1882 and ‘ACT715-R/LM1882-R are 20-pin TTL-input compatible devices capable of generating Horizontal, Vertical and Composite Sync and Blank signals for televisions and monitors.
		Four additional signals can also be made available when Composite Sync or Blank are used.
		These signals can be used to generate horizontal or vertical gating pulses, cursor position or vertical Interrupt signal.
	www.hardwarehacking.com /category/electronics/programmable-video-sync-generator (315 words)

	Fast Repeat Key
		I began by writing a program that copied the OS keyboard interrupt routine from ROM into RAM, changed the value stored into SRTIMR and, of course, altered the interrupt vector to point to the new routine.
		interrupt handler in a different ROM location (this wasn't really a problem, since I could check the "reserved" interrupt vector to find out where it was), but it was three, Yes, three times as long as the handler in the
		After a few more attempts, including one that tried to determine which OS you had by checking the size of the interrupt handler, I finally got it right.
	www.cyberroach.com /analog/an16/fast_repeat.htm (611 words)

	vertical blank interrupt - Article and Reference from OnPedia.com
		A vertical blank interrupt (or VBI) is a programming technique used in some systems, notably video games and consoles, to allow program code to be run in the periods when the display hardware is turned off, waiting for the TV to complete its vertical blank, which takes about 20 uS.
		Since the vertical blank period occurs regularly every 25th or 30th of a second (depending on the standard), timing the code to run during this period guarantees a regular "heartbeat" which is useful for timing-dependent functions.
		Simple routines like reading the joystick or updating the display can be placed in the VBI, and then basically ignored while the main program runs.
	www.onpedia.com /encyclopedia/vertical-blank-interrupt (243 words)

	horizontal blank interrupt - Article and Reference from OnPedia.com
		A horizontal blank interrupt is a programming technique used in some systems, notably video games and consoles, to allow program code to be run in the periods when the display hardware is turned off, waiting for the TV to complete its horizontal blank, which takes about 10 uS.
		The technique was only really useful before the entire display could be addressed directly with high speed CPUs attached to large frame buffers, that is, in the days of 8-bit systems.
		By changing the values of the palette registers during the HBI, the system could select a new set of four colors on every line, leading to a number of "rainbow" displays with all 256 colors on screen (four per line).
	www.onpedia.com /encyclopedia/horizontal-blank-interrupt (220 words)

	Timing a Flip
		This amount of time is determined empirically (unless the monitor refresh rate is known) at driver initialization and on mode changes by polling until the display is in vertical sync, and then polling until it is not in vertical sync.
		If the line number of the scan line is not available, it may be possible to verify that the scan line has passed from display through vertical blank and back into display.
		The ability to check whether the scan line is in display or in vertical blank should be available on all display cards, but the scan-line number may not be.
	www.osronline.com /ddkx/graphics/ddraw_4eqv.htm (825 words)

	II.D· INTERRUPT SYSTEM (Site not responding. Last check: 2007-10-26)
		Since any of these interrupts will cause the processor to jump to the same NMI address, the system also has NMI status bits which may be examined by the processor to determine which source caused the NMI interrupt.
		Two of the interrupt enable bits (bits 6 and 7 of NMIEN) are cleared automatically during system power turn on and therefore these NMI interrupts are initially disabled (masked), preventing any power turn on service routine from being interrupted before proper initialization of registers and pointers*.
		These NM interrupt functions are each separated in time (to prevent overlaps) and converted to pulses by the system hardware, in order to supply NMI transitions required by the microprocessor logic.
	homepage.ntlworld.com /kryten_droid/Atari/800XL/atari_hw/atari_hw_02d.htm (858 words)

	ATR: Chapter 10 - System Interrupts
		When an NMI interrupt occurs, the hardware register NMIST [$D40F] is examined to determine what type of interrupt occurred.
		INTERRUPT REQUESTS (maskable interrupts (IRQs)) When an IRQ interrupt occurs the hardware register IRQST [$D20E], the PIA status registers, PACTL [$D302] and PBCTL [$D303] are examined to determine what caused the interrupt.
		The result is that reading the register does not reveal the enabled interrupts but the interrupts pending.
	atrey.karlin.mff.cuni.cz /~pavel/atari/atr10.html (1084 words)

	Vertical blank interrupt: Definition and Links by Encyclopedian.com
		...Vertical blank interrupt Vertical blank interrupt A vertical blank interrupt...TV to complete its Vertical-blank Vertical blank vertical blank, which takes about 20 uS.
		Since...its Vertical-blank Vertical blank vertical blank, which takes about 20 uS.
		Post a link to definition / meaning of " Vertical blank interrupt " on your site.
	www.encyclopedian.com /ve/Vertical-blank-interrupt.html (323 words)

	Raster interrupt in TutorGig Encyclopedia
		A 'raster interrupt' is a computer interrupt signal that is utilized for display timing purposes.
		An interrupt would be set to trigger when a given screen line was refreshed, and the interrupt routine could then reload the chip's registers.
		The Nintendo Entertainment System's PPU graphics chip did not support true raster interrupts - an interrupt could be set to trigger during the vertical blank interval, but not at any arbitrary scan line - and instead required polling of a "hit flag" that indicated when the first sprite was being drawn.
	www.tutorgig.com /ed/raster_interrupt (364 words)

	Sean Riddle's Home Page - Lines at top of screen
		Each game has a routine that runs during the vertical blanking interval (the time it takes the beam to go from the bottom of the screen back up to the top) that sets the color registers.
		The watchdog was being cleared outside of the vertical blank interval, so the lines showed up whereever the screen was being drawn at that time.
		The only problem is that when there's a lot of blitting going on (the start of a Robotron wave, for example), the vertical blank interrupt service routine gets delayed a bit, causing the glitch to appear even lower.
	members.cox.net /seanriddle/lines.html (1050 words)

	[No title]
		During the interrupt, pushing of registers to be used should be performed by the interrupt routine.
		If a RET is used as the final instruction in an interrupt routine, interrupts will remain disabled unless a EI was used in the interrupt routine or is used at a later time.
		Due to the fact that keypad "bounce"* is virtually always present, software should expect this interrupt to occur one or more times for every button press and one or more times for every button release.
	members.tripod.com /~jaymzroo/gb/spec.htm (3311 words)

	atari:atari_ste_developer_information_addendum [Markus Fritze (MMM)]
		This is done at vertical blank interrupt time by writing to the three eight-bit video display address registers to define a twenty-four-bit pointer into memory.
		Next, both vertical and horizontal blanking interrupt vectors are captured and the horizontal blanking interrupt is enabled in counter mode.
		Regardless of how you manage your interrupts, there is more you should know: the signal goes from “active” to “idle” when the DMA sound chip has fetched the last sample in the frame.
	www.sarnau.info /atari:atari_ste_developer_information_addendum (4667 words)

	ANTIC (Site not responding. Last check: 2007-10-26)
		Vertical blank (VBLANK) is the time during which the electron beam returns back to the top of the screen in preparation for the next frame.
		In addition to a Vertical Blank Interrupt, which allows the microprocessor to synchronize to the vertical TV display, this system also provides a Wait for Horizontal Sync (WSYNC) command that allows the microprocessor to synchronize itself to the TV horizontal line rate.
		Each instruction defines the type (alpha character or memory map) and the resolution (size of bits on screen) and the location of data in memory to be displayed for a group (1 to 16) of lines.
	homepage.ntlworld.com /kryten_droid/Atari/800XL/atari_hw/antic.htm (2476 words)

	[No title]
		When the vertical blank and timer interrupts occur at the same time, a level 6 interrupt is triggered.
		Port C D7: (Not connected) D6: (/WDC) D5: Screen display (1= blanked, 0= displayed) D4: (ADC2) D3: (ADC1) D2: (ADC0) D1: (CONT) D0: Sound section reset (1= normal operation, 0= reset) CONT is connected to the sprite generator.
		Interrupts /INT - From the YM2151 timers /NMI - Triggered when a sound command is issued by the main CPU.
	cgfm2.emuviews.com /txt/loftech.txt (2517 words)

	Horizontal blank interrupt: Definition and Links by Encyclopedian.com
		...Horizontal blank interrupt Horizontal blank interrupt A horizontal blank...TV to complete its Horizontal-blank Horizontal blank horizontal blank, which takes about 10 uS....to a number of rainbow displays with all 256 colors on screen (four per line).
		See also: horizontal blank interrupt i Acanthodii Acanthodii - extinct ...
		Post a link to definition / meaning of " Horizontal blank interrupt " on your site.
	www.encyclopedian.com /ho/Horizontal-blank-interrupt.html (320 words)

	Re: Interrupts
		IE0 is to enable/disable interrupts from a lightpen/mouse connected to the v9938/58.
		However, in the MSX system the mouse is read through the PSG and a lightpen is most of the time not connected (you'll have to solder on your VDP to do that...
		It's supposed to be the contents of the > data bus at the moment of the interrupt being acknowledged.
	www.mail-archive.com /msx@stack.nl/msg08589.html (292 words)

	[No title]
		If the window is used and a scan line interrupt disables it (either by writing to LCDC or by setting WX > 166) and a scan line interrupt a little later on enables it then the window will resume appearing on the screen at the exact position of the window where it left off earlier.
		This way, even if there are only 16 lines of useful graphics in the window, you could display the first 8 lines at the top of the screen and the next 8 lines at the bottom if you wanted to do so.
		WX may be changed during a scan line interrupt (to either cause a graphic distortion effect or to disable the window (WX>166)) but changes to WY are not dynamic and won't be noticed until the next screen redraw.
	homepage.mac.com /jschrier/gameboy/GBSPEC.TXT (4292 words)

	Interrupts
		Hi there, I'd like to know once and for all what the exact meaning of the IE bits of registers #0 and #1 is. As Laurens pointed out some days ago bit #5 (IE0) of regiter #1 is the enable bit for the vertical blank interrupt (ie the VDP reaching line 212).
		Here's the second one: if I use interrupt mode 2 what are the contents of the lsb that forms (with register I being the msb) the address whose contents point to the actual interrupt routine?
		It's supposed to be the contents of the data bus at the moment of the interrupt being acknowledged.
	www.mail-archive.com /msx@stack.nl/msg08586.html (158 words)

	What is VIXN
		To meet these requirements, you must deliver low interrupt latency; that is the time between when the interrupt happens and when the user code executes as a consequence.
		Traditionally, ITEX has offered interrupt services that allow a user thread to be awakened by a Coreco Imaging hardware module interrupt.
		You are assured that if an operation had to occur during a brief vertical blank, it would always do so.
	www.coreco.com /Web/kb.nsf/AllDocsById/8F440BFCE3A2E3D2852569F100772B9B?OpenDocument&Lang=Gb (496 words)

	De Re Atari - Chapter 8
		Just as importantly, these interrupts occur during that period of time when the screen has been blanked, so that changes made during this period will not be immediately seen on the display.
		These two vectors were put into RAM to allow programmers to trap the vertical blank service routine and use the 60-Hertz interrupt for their own purposes.
		This signal is called vertical blank, and in television sets it is the cue to turn off the electron beam and begin retracing to the top of the screen in preparation for another frame.
	evilbill.org /Atari/8-Bit/dere/chapt8.html (9363 words)

	libgba: gba_interrupt.h File Reference
		To acknowledge processing interrupts, set IF to the value of the interrupt handled.
		When bit 0 is clear, all interrupts are masked.
		When it is 1, interrupts will occur if not masked out in REG_IE.
	devkitpro.sourceforge.net /onlinedocs/libgba/a00033.html (182 words)

	SMS Power! - Forums - View topic - Vdp Interrupts?
		What's happening is that in both games, the interrupt is either not being triggered (more likely), or something is not being emulated correctly inside of the interrupt handler.
		If so, I presume your interrupt code is mostly functional and Transbot and Happy Looser both do something to cause the interrupt not to be triggered.
		Since they both use line interrupts, it might be that they set their "frame completed" flag in the line interrupt instead of the vertical blank interrupt.
	www.smspower.org /forums/viewtopic.php?p=36419 (406 words)

	Paul Hsieh's Flicker Free Animation page
		This works because there is an interval of time (called vertical blanking) when the monitor's scan gun has to literally reposition itself at the start of the display.
		During the vertical blanking stage none of the display is being refreshed, so modification of graphics memory will not cause any sort of flickering or tearing.
		This is well known technique where you update a non-display portion of graphics memory, the back buffer, then repoint the graphics hardware's display memory to it at the start of vertical blank.
	www.azillionmonkeys.com /qed/flicker.html (1822 words)

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