[Coco] CoCo video?

jdaggett at gate.net jdaggett at gate.net
Sun Jan 29 22:30:31 EST 2006


Yes there was. MC6844. This chip better interfaces with the MC6809 and 
not the MC6809E. The MC6809 has an input labled DMABREQ. Asserting 
this pin low will suspend the MC6809 execution for 16 cycles. Then the 
MC6809 will execute one cycle. Thus there is an alternating of 16 to one 
cycle ratio for DMA access. 

With some external logic this can be done with the MC6809E. 


On 29 Jan 2006 at 18:52, Neil Morrison wrote:

From:           	"Neil Morrison" <neilsmorr at hotpop.com>
To:             	"CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Subject:        	Re: [Coco] CoCo video?
Date sent:      	Sun, 29 Jan 2006 18:52:09 -0800
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> Wasn't there some sort of DMA chip for the 6800 series? 
> Neil
> ----- Original Message ----- 
> From: "Gene Heskett" <gene.heskett at verizon.net>
> > The 6x09 doesn't, without extensive hardware help, support dma, so the 
> > max transfer is going to be someplace in the 12 seconds per megabyte 
> > moved area...
> -- 
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