Hi Everybody, A few people have expressed interest in a re-creation of the DVI, so I thought I would start a new thread. My plan is to recreate the DVI, providing support for everything that the DVI used to support (Video / Disk - And extending that to the modern world. Disk support would be as far as possible 5.25 and 3.5", with the ability to load 'slices' from a SD card in the same way that the GoTec allows us to.
Video support would be composite 40 char / 80 char and some way of supporting HDMI, so it would plug into a modern display. To provide HDMI, it would likely have a raspberry Pi in there - that allows us to emulate the entire DVI function. No need for a Z80 (They are out of manufacture now anyway) - Connectivity to the M100 would be via the GPI connection into the Pi. Now - I need to understand some facts, and the quickest way to get them correct, is to publish something on the Internet :-) - My understanding of the DVI interface is that it uses something like an 8255 PIO communicating with the M100 across the system bus on the underside of the machine. - A review of the M100 code suggests that there are a heap of DVI functions built in around address 0x767D. - It looks like the DVI implements a status port at IO address 0x82 and some data ports at 0x80 and 0x81. The DVI implements some sort of buffer using these ports to allow comms to / from the M100. - On bootup, if the DVI is present, it sends some initialization code to the M100 which is loaded at 0xE000 and executed. I suspect this then loads the Disk Basic updates from the FDD to the M100 modifying hooks in the various jump tables. I haven't found a disassembly of the IPL code, or the Disk Basic extensions - These are likely key to understanding the comms, so that it can be emulated. The nice thing about this project, is that it wouldn't rely on a boot disk. Everything would be in software. Does anybody have any pointers? Kindest regards, Doug Jackson em: [email protected] ph: 0414 986878 Follow my amateur radio adventures at vk1zdj.net
