1 Nov
2022
1 Nov
'22
5:01 p.m.
Hi Paul. Who “corrected” you about DMA input? I’d like to read about that as nothing i
read about the DZ mentioned that. Got any Cites?
Sent from my iPhone
On Nov 1, 2022, at 09:01, Paul Koning via cctalk
<cctalk(a)classiccmp.org> wrote:
On Oct 30, 2022, at 2:49 PM, Wayne S via cctalk
<cctalk(a)classiccmp.org> wrote:
The difference between dz and dh interfaces is that the dh used dma instead of interrupts
to get characters to the cpu. It would be transparent to any software.
No, it doesn't. I was confused about this but was recently corrected.
The DH11 does DMA output, but not DMA input. I don't know any DEC serial port
devices that have DMA input; it would make very little sense to do that since input
generally is one character at a time. Block mode terminals do exist in DEC's world
but they are rare, and even those are hard to operate with simple DMA.
DZ is programmed I/O in both directions, which makes the difference. In typical usage,
the bulk of the terminal traffic is output, so doing that with DMA is a big win.
paul