From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2004-06-21 20:12:24
On Mon, Jun 21, 2004 at 07:51:54PM +0200, Christian Johansson wrote: > > Well, actually, the biggest problem is badlines - and they're 40 us > > long even in 2 MHz mode. In 80 column mode with the VIC screen closed > > it's possible to use 9600 bps though. > > I'm not very familiar with badlines. Does that problem exist even if I blank > the screen in 40-column mode? No. In 2 MHz mode, there are no badlines, but the system will run at 1 MHz during memory refresh (5 slow cycles on every rasterline), making the total number of cycles per raster line equal 63*2-5 on PAL systems and 65*2-5 on NTSC. Maybe MagerValp was thinking the TED, which doesn't show garbage on the screen, but slows down the processor to 1 MHz during graphics DMA. The TED also has two badlines for every line of text. > What I want to know is if the Hug routine I posted in my > previous email could perhaps be used to get at least 4800 bps by making some > small modifications to it. You may need to take the DRAM refresh cycles into consideration. The bit time for 4800 bps is 17734472/18/4800 = 205 slow cycles on the PAL C128 and 14318181/14/4800 = 213 slow cycles on the NTSC C128. Okay, maybe you can ignore the DRAM refresh even at 9600 bps. Marko Message was sent through the cbm-hackers mailing list
Archive generated by hypermail pre-2.1.8.