dlleigh@mit-amt.MEDIA.MIT.EDU (Darren L. Leigh) (04/27/88)
So, what do we know about the RGB connector on the Amiga? The signal specs aren't in the hardware manual or the Schematics and Expansion specs. I'd really like to know how all the signals work, especially the sync inputs. ============================================================================= Darren Leigh dlleigh@media-lab.mit.edu 362 Memorial Dr. mit-amt!dlleigh Cambridge, MA 02139 "Lost $1000 when I sold my PC clone. It was worth it."
hedley@cbmvax.UUCP (Hedley Davis) (04/28/88)
In article <2391@mit-amt.MEDIA.MIT.EDU> dlleigh@media-lab.UUCP (Darren L. Leigh) writes: >So, what do we know about the RGB connector on the Amiga? The signal >specs aren't in the hardware manual or the Schematics and Expansion >specs. > >I'd really like to know how all the signals work, especially the sync >inputs. > The sync outputs are basically just normal HSYNC and VSYNC outputs, active low. The hardware is actually tristate logic which is not driven when the machine first boots. If some signals are driving the sync inputs at boot time, the system detects this and enters the infamous genlock mode. In this case the system will allow its vertical and horizantal beam position counters to be affected by these inputs, but only over a very small window. Basically you can shorten or lengthen a horizontal line by 280 ns via by asserting HSYNC in the vicinity where it would have otherwise been asserted. Similar comments apply to VSYNC on a line basis. Failure to assert these signals will result in nothing as the internal counters will simply wrap to zero and thus the amiga will continue to run and display normal video, but without syncs. In addition, there is XCLK, and XCLKEN. XCLKEN is a DC signal which can be used to tell the amiga to ignore its internal 28.6363 Mhz clock, and use the signal at XCLK instead. This is the system clock. Driving it with anything other than something approximating a 28 Mhz clock will most definitely trash your system. Genlocks phaselock the color burst signal coming from an external video device up to 28 Mhz to drive this input. This allows full pixel synchronization between amiga video, and external video. Each of these four signals is TTL level. Hedley