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Phillip M Gallo
10/25/05 14:36
Read: 776 times
Torrance
USA


 
#102942 - Video Timing.
Responding to: Jan Waclawek's previous message
Jan,

To tighten up the Video Timing evaluation you must consider that Video generation runs as a Timer Interrupt.

To achieve the determinancy required for sharp video, Craig came up with a method which uses the # of timer ticks since interrupt to index into a path of NOP's to assure consistent entry into Video Interrupt.

As you note Active Video (display field generation) is where all the overhead occurs.

There are three basic types of video line being generated:
1)Black Line; 2)Displaying Line; 3)Synch Line;

Each line begins with a Horizontal Sync pulse within a Blanking Interval.

Both Horiz. Sync and Blanking occur as a port write and timer reload and (pushes/pops). Consequently, the greatest portion of Hsync and blanking intervals ~(10.8us every line) accrues to the foreground and does for every line generated.

Black lines (above and below the display field) and BLANK lines (occuring as 1/2 lines during Vertical Sync) also occur as a port output and timer reload, so the greatest portion of any "static" line also accrues to the foreground.

Finally, for each displaying line, the left and right black borders are also port writes and timer reload. In fact the 256 pixels within each displaying line occurs in a 41us interval between left and right borders. This is to avoid CRT edge effects like "pin cushion" distortion.

So the ballpark max latency in response to an alternative interrupt or foreground event is the 41us + Int Arbitration/overhead (for Horizontal displaying lines).

regards,
p




List of 67 messages in thread
TopicAuthorDate
8051 8-bit computer      Jeff Corr      10/19/05 06:09      
   (or z80)      Jeff Corr      10/19/05 06:10      
   8051 computer      Craig Steiner      10/19/05 08:05      
      I never cringe on a "fun exercise" I do,      Erik Malund      10/19/05 08:21      
         awesome?      Jeff Corr      10/19/05 11:09      
            Computer      Craig Steiner      10/19/05 11:45      
               8051 Computer.      Arif Deshmukh      10/19/05 11:57      
               Minor corrections      Craig Steiner      10/19/05 20:31      
                  11MHz?      Jan Waclawek      10/20/05 00:59      
                     Not sure      Craig Steiner      10/20/05 08:07      
                        Congratulations      José Félix Díaz Ivorra      10/20/05 11:25      
                           Actually it's teh same        Craig Steiner      10/20/05 12:38      
                        11MHz      Phillip M Gallo      10/20/05 11:33      
                        Re: 8051 computer      Valentin Angelovski      10/20/05 18:37      
                           Just us      Craig Steiner      10/20/05 21:12      
                              Project Team      Sriharsha Vedurmudi      10/21/05 00:42      
                                 me tried      Oleg Sergeev      10/21/05 01:13      
                                    thoughts on project      Jeff Corr      10/21/05 02:28      
                                       What is a true multitasking controller?      Russell Bull      10/21/05 03:54      
                                          multitasking controller      Jan Waclawek      10/21/05 04:05      
                                             video      Oleg Sergeev      10/21/05 06:30      
                                             continued..      Jeff Corr      10/22/05 19:37      
                                          continued..      Jeff Corr      10/22/05 19:35      
                                             I don't think so      Craig Steiner      10/22/05 20:02      
                                                color display?      Jeff Corr      10/22/05 21:36      
                                                   Predko Video      Phillip M Gallo      10/22/05 23:17      
                                                      yes      Jeff Corr      10/23/05 13:38      
                                                      video, timing, speeds etc.      Jan Waclawek      10/25/05 10:28      
                                                         Video Timing.      Phillip M Gallo      10/25/05 14:36      
                                                            6.2MHz pixel clock?      Jan Waclawek      10/26/05 01:20      
                                                               Pixel Clock      Phillip M Gallo      10/26/05 11:39      
                                                                  pix clock      Phillip M Gallo      10/26/05 15:10      
                                                                  overclocking      Jan Waclawek      10/26/05 15:20      
                                                                     pad pixels      Phillip M Gallo      10/26/05 16:15      
                                                just a suggestion      Erik Malund      10/24/05 11:54      
                                                   Speed      Craig Steiner      10/24/05 13:22      
                                                      DS'4x0      Phillip M Gallo      10/24/05 17:26      
                                                      DIP / surface mount      Jeff Corr      10/24/05 19:32      
                                                         a 100MHz chip in a perf board? methinks      Erik Malund      10/25/05 06:33      
                                                Hardware multitasking      Sasha Jevtic      10/24/05 17:49      
                                                Multitasking redefined      Dan Henry      10/25/05 06:55      
                                             Misplaced self belief...      Donald Catto      10/24/05 03:01      
                                                Daunting?      Andy Neil      10/24/05 04:08      
                                                breadboarded      Jeff Corr      10/24/05 12:05      
                                                   TRS-80      Andy Neil      10/24/05 13:07      
                                                      TRS80?      Jan Waclawek      10/24/05 14:45      
                                                         in the beginning there was ..      Erik Malund      10/24/05 14:52      
                                                         TRS-80 Info      Phillip M Gallo      10/24/05 14:54      
                                                            Man those were the days.      Jon Ledbetter      10/24/05 15:22      
                                                               That fast?      Craig Steiner      10/24/05 16:00      
                                                                  More retroinfo      José Félix Díaz Ivorra      10/24/05 16:49      
                                                                  TRS-80 forward speed.      Phillip M Gallo      10/24/05 17:11      
                                                                  Like I said, It was a long time ago      Jon Ledbetter      10/25/05 07:48      
                                                               hrm      Jeff Corr      10/24/05 19:16      
                                                                  TRS80 model 1 speed...      Rob Vassar      10/24/05 19:47      
                                                         TRS80      Jan Waclawek      10/25/05 07:55      
                                                            You think?      Craig Steiner      10/25/05 08:38      
                                                               OK so both      Jan Waclawek      10/25/05 10:30      
                                                   No pictures yet      Craig Steiner      10/24/05 13:27      
                                                      Video Capture Card?      Jon Ledbetter      10/24/05 13:31      
                                                         Nope      Craig Steiner      10/24/05 13:47      
                                                      video output      Jeff Corr      10/24/05 19:27      
                                                Qui?      Rob Vassar      10/24/05 18:45      
                                                Multitasking      Grant Beattie      10/25/05 10:44      
                                                   Real Time and Multi Tasking      Ian Bell      10/25/05 15:47      
                                             Maybe whomever has "no idea what I'm tal      Erik Malund      10/24/05 11:51      
      It's probably at least fast enough ...      Richard Erlacher      11/11/05 00:04      

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