Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
10/25/05 20:36
Read: times


 
#102942 - Video Timing.
Responding to: ???'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            01/01/70 00:00      
   (or z80)            01/01/70 00:00      
   8051 computer            01/01/70 00:00      
      I never cringe on a "fun exercise" I do,            01/01/70 00:00      
         awesome?            01/01/70 00:00      
            Computer            01/01/70 00:00      
               8051 Computer.            01/01/70 00:00      
               Minor corrections            01/01/70 00:00      
                  11MHz?            01/01/70 00:00      
                     Not sure            01/01/70 00:00      
                        Congratulations            01/01/70 00:00      
                           Actually it's teh same            01/01/70 00:00      
                        11MHz            01/01/70 00:00      
                        Re: 8051 computer            01/01/70 00:00      
                           Just us            01/01/70 00:00      
                              Project Team            01/01/70 00:00      
                                 me tried            01/01/70 00:00      
                                    thoughts on project            01/01/70 00:00      
                                       What is a true multitasking controller?            01/01/70 00:00      
                                          multitasking controller            01/01/70 00:00      
                                             video            01/01/70 00:00      
                                             continued..            01/01/70 00:00      
                                          continued..            01/01/70 00:00      
                                             I don't think so            01/01/70 00:00      
                                                color display?            01/01/70 00:00      
                                                   Predko Video            01/01/70 00:00      
                                                      yes            01/01/70 00:00      
                                                      video, timing, speeds etc.            01/01/70 00:00      
                                                         Video Timing.            01/01/70 00:00      
                                                            6.2MHz pixel clock?            01/01/70 00:00      
                                                               Pixel Clock            01/01/70 00:00      
                                                                  pix clock            01/01/70 00:00      
                                                                  overclocking            01/01/70 00:00      
                                                                     pad pixels            01/01/70 00:00      
                                                just a suggestion            01/01/70 00:00      
                                                   Speed            01/01/70 00:00      
                                                      DS'4x0            01/01/70 00:00      
                                                      DIP / surface mount            01/01/70 00:00      
                                                         a 100MHz chip in a perf board? methinks            01/01/70 00:00      
                                                Hardware multitasking            01/01/70 00:00      
                                                Multitasking redefined            01/01/70 00:00      
                                             Misplaced self belief...            01/01/70 00:00      
                                                Daunting?            01/01/70 00:00      
                                                breadboarded            01/01/70 00:00      
                                                   TRS-80            01/01/70 00:00      
                                                      TRS80?            01/01/70 00:00      
                                                         in the beginning there was ..            01/01/70 00:00      
                                                         TRS-80 Info            01/01/70 00:00      
                                                            Man those were the days.            01/01/70 00:00      
                                                               That fast?            01/01/70 00:00      
                                                                  More retroinfo            01/01/70 00:00      
                                                                  TRS-80 forward speed.            01/01/70 00:00      
                                                                  Like I said, It was a long time ago            01/01/70 00:00      
                                                               hrm            01/01/70 00:00      
                                                                  TRS80 model 1 speed...            01/01/70 00:00      
                                                         TRS80            01/01/70 00:00      
                                                            You think?            01/01/70 00:00      
                                                               OK so both            01/01/70 00:00      
                                                   No pictures yet            01/01/70 00:00      
                                                      Video Capture Card?            01/01/70 00:00      
                                                         Nope            01/01/70 00:00      
                                                      video output            01/01/70 00:00      
                                                Qui?            01/01/70 00:00      
                                                Multitasking            01/01/70 00:00      
                                                   Real Time and Multi Tasking            01/01/70 00:00      
                                             Maybe whomever has "no idea what I'm tal            01/01/70 00:00      
      It's probably at least fast enough ...            01/01/70 00:00      

Back to Subject List