woodside@ttidca.TTI.COM (George Woodside) (06/07/90)
In article <9006062131.AA12027@kaukau.comp.vuw.ac.nz> ST131BAP@ST1.VUW.AC.NZ writes: ...[edited]... >.... One minor niggle though. The information >I have recieved states that Spectrum stores three palettes per scan line. >How are these palettes used? I can understand the idea of Display >List Interrupts changing the palette data at the end of each scan line >but dividing the scan lines in three produces an uneven no. of pixels >for each palette set. Can anyone help me on this? Spectrum displays use tight, and precisely synchronized timing loops to change the color registers on the fly as the picutre is displayed. The first set of 16 colors is loaded as the raster is in the overscan area, and is set prior to the first pixel on the line. Then, as the raster traverses the scan line, the registers are continuously being loaded. One register changes each 10 pixels, as I recall. Any software attempting to deal with a spectrum file must, therefore, keep itself in synch with the current values of the registers as it works through the scan line, and trrough the picture. The top line is always blank, and used to synch up the registers with the timing loop. The remaining 199 lines get the sets of 64 pallette entries each. -- * George R. Woodside - Citicorp/TTI - Santa Monica, CA * * Path: woodside@ttidca * * or: ..!{philabs|csun|psivax}!ttidca!woodside *
ST131BAP@ST1.VUW.AC.NZ (06/08/90)
Thanks every one for your kind help. I now have enough to keep me
happy and burbling for a while. One minor niggle though. The information
I have recieved states that Spectrum stores three palettes per scan line
. How are these palettes used? I can understand the idea of Display
List Interrupts changing the palette data at the end of each scan line
but dividing the scan lines in three produces an uneven no. of pixels
for each palette set. Can anyone help me on this?
Anyway thanks very much for the present help and thanks in
advance for any future help...
N.B. You know in two days of recieving email messages I have learn't
more than in three months of asking the local 'experts'.
There is a moral somewhere in that.....
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| P.R.Banks (aka BANKSie!) ST131BAP@vuwst2.vuw.ac.nz (Archimedes owner) |
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Hey! Don't knock it. It was the best I could do in five minutes!