Posted By
MMS
on 2019-12-03
11:50:22
 |  Re: TED Rastertiming specs
Also there is a good article about the TED from TLC (Levente) in C= Hacking News
While it starts as a basic introduction of TED (and similaritis to VIC-II), it gives some insight about the timings too
(Levente's article is at the end of the mag)
http://www.ffd2.com/fridge/chacking/c=hacking12.txt
QUOTE
The TED IC is able to generate both PAL and NTSC compatible signals from
a single IC. Only the crystal need be changed to go from one standard to
the other. In PAL mode, there are 312 lines hown, while NTSC only has 262
lines of display. The line synchronization is the same in either PAL or
NTSC mode. It's always 57 clock cycles per rasterline. The TED divides
the supplied crystal frequency by 20 for PAL display and by 16 for NTSC.
For the serious video programmer, raster interrupts are implemented as on the
VIC-II. However, the 0 line of the register corresponds to the first line
of the character screen area, not the top of the border. In addition, the
current raster line can be read from TED registers. you can modify the
counter as well. Doing so will most likely affect the screen display. As
a bonus, the horizontal location of the raster can be read and modified in
the same way. Unfortunately, these registers provide the basis for most
effects, as the TED can't handle sprites.
@(A): Running The Show
As earlier mentioned, the TED IC does more than produce graphics. One of
its tasks involves generating the clock signal for the 7501/8501
microprocessor. The clock is not constant, as it switches from from
885 kHz and twice that speed, 1.773 Mhz. The speed depends on TED's current
task. It generates the slower clock signal when refreshing DRAM or fetching
data for the video screen. Otherwise, the high clock signal is generated.
The user can disable fast clock generation via a register. The end result
is a machine that operates at approximately 1 MHz, as the CPU runs in slow
mode while the screen is displayed, and operates in fast mode when the
TED starts drawing the top and bottom borders.
UNQUTE
|
