Post by thread:Video output from pic -- Commodore 8563 video chip

One possible way of generating nice RGB video output from a PIC (for CGA-style monitors) is to use the Commodore 8563 video chip (used in the Commodore 128 computer). I have just stumbled upon a web site that lists them for sale at $17.95ea but I have no idea of quantity available. With the addition of a crystal for the dot clock and two 4416 or 41464 DRAM chips you'll have a video system which can be controlled using 11 I/O pins (D0-D7, /CS, R/W, and A0). Note that the DRAMs sit on their own bus and the main CPU need not worry at all about them. The 8563 is a cool chip--too bad I don't know of anything else like it. It's designed for 80-column video, but it can also be used in hires graphics mode. Instead of using attribute bytes for foreground and background color as does the CGA, there is one background color register and the attribute bytes provide reve rse video, underlining, character-set-select, and blinking. Now all I need to do is find an application for it...

>From distant memory, the Motorola 6847 should be reasonably useful. I made a vdu with one of these many (many) years ago. AFAIR this has its own character generator and only needs a RAM to scan. While "proper" designs will dual port the RAM a lash up could probably use a PIC addressing it directly from otherwise floating port pins. May be too many pins needed for an 18 PIN PIC unless eg serial shift registers were used for addressing. Russell McMahon From: John Payson <spam_OUTsupercatTakeThisOuTCIRCAD.COM> >One possible way of generating nice RGB video output from a PIC (for CGA-style >monitors) is to use the Commodore 8563 video chip (used in the Commodore 128 >computer). I have just stumbled upon a web site that lists them for sale at >$17.95ea but I have no idea of quantity available. >

Russell McMahon wrote: > >From distant memory, the Motorola 6847 should be reasonably useful. > AFAIR this has its own character generator and only needs a RAM to > scan. True. Was used in the 6502-based Acorn Atom. That dates me! I hated it for its 60Hz refresh rate and caps-only text. Video RAM accessed by badly-implemented dual-porting: if the 6502 accessed it when the 6847 did, the latter lost and put 'snow' on the screen. The OS waited for flyback to place video data. If your cunning and run the 6502 and 6847/6845/6545 off the same clock, you can synchronise them so they interleave accesses and never cause snow! But thats another story.