If you scroll down to the bottom of Lukasz Jokiel's blog page on how to connect an RGBtoHDMI to an STe including a modified Amiga 12-bit buffer board there are a couple of sources for CSYNC in an STe:
A) pin 2 of U403 (MC1377) or pin 6 of U211 (74LS04) in RF-modulator equipped STe computers.
- ste_csync.png (141.59 KiB) Viewed 5 times
So there are STe machines with RF-modulators, STe machines without (typically French machines from what I've heard). There's also the issue of PAL machines in Western Europe and NTSC machines in North America -I don't know if that makes any difference in regards to the CSYNC signal.
Since I'm working on an STe/MegaSTe compatible 12-bit buffer board for use with RGBtoHDMI I'm considering if I should include a small circuit for generating CSYNC to ensure everybody gains access to that signal. I've come across several ways to generate CSYNC if there isn't one available:
- Building a passive sync combiner (simple, transistor-based circuit)
- circuit built around a 74LS86
- quick and dirty video sync combiner built around the CD4077
- building a clean Atari ST RGB CSYNC signal (FPGA based)
With my limited knowledge I'm wondering if obtaining CSYNC externally (using one of the above circuits for instance) will put less of a strain on the Atari circuitry and create a cleaner/better signal, or if it'll just be excessive and not make any difference?
I also want to know if CSYNC is guaranteed available on all STe and MegaSTe machines by tapping into their existing circuitry?
I've examined the MegaSTe schematics and see it's very similar to the STe schematics. Are there MegaSTe machines without RF-modulators as well?
