Subject:
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Re: spi serial port.
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 28 Jun 1997 03:56:34 GMT
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Original-From:
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Remi Desrosiers <(harlock@videotron)antispam(.ca)>
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Viewed:
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1431 times
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At 20:57 97-06-26 -0400, you wrote:
> e. crispell wagner spake unto the ether:
>
> > Has anyone done any work on 'networking protocol' using the spi port on
> > the handy board to communicate with other 6811's/handy boards/mini-boards?
> > Any information regarding the spi for serial communications or a simple
> > network would be appreciated.
>
> Please don't laugh at me, folks, you may not believe it,
> but this problem was solved in 1982 by the ill-fated Coleco ADAM
> computer.
>
> The ADAM's peripherals (disk drive, tape drive, printer,
> serial/parallel card, keyboard) were attached to a token-passing
> network using the SPI port of Motorola 6801 microcontrollers.
> This network was called ADAMnet. Peripherals were connected by
> simple 6-conductor phone cable (which had a single serial data line,
> +5V and ground so low-load peripherals like keyboards didn't need
> a separate power supply, and a network RESET line), and you could
> daisy-chain them. A "Master" 6801 sat on the ADAM motherboard and
> interfaced between the Z80 CPU and the network devices. User device
> I/O requests were routed to the appropriate peripheral by broadcasting
> a token packet to the network; all devices would receive the token,
> their firmware would decide if it was for them or not, and they would
> either process the request or else go to sleep until the responding
> peripheral had competed the I/O. The Motorola 68xx family of
> microcontrollers all implement this network-capable SPI port: as long
> as the network data is packet-oriented (so single transactions take
> place in a continuous stream of serial bytes), a network device can
> put itself to sleep (i.e., disable its response to the SPI RxD
> interrupt) and stay asleep while someone else uses the bus, until there
> is a certain number of clock cycles of inactivity, at which point the
> RxD interrupt magically re-enables and the peripheral waits for another
> token packet.
>
> The 6811 can be used in exactly this way (in fact, I've toyed
> with the idea of writing some ADAMnet firmware for the Handy Board, so
> I could have an ADAM-controlled robot board).
>
> For this kind of network protocol to work, however, you would
> need some kind of "Master" to regulate access to the network, to
> prevent two network nodes from trying to talk at the same time.
> There may be other viable network topologies; I have not studied
> networking except to learn about how it works on the Coleco ADAM.
> Apologies in advance for any amateur's ignorance I may be displaying.
>
> If there is any interest in further technical details about the
> ADAMnet SPI bus, please let me know and I'll put something together.
> (It might not be immediately, but certainly before the end of the summer.)
>
> *Rich* (whose hobby system is the Coleco ADAM)
>
> --
> Richard F. Drushel, Ph.D. | "Aplysia californica" is your • taxonomic
> Department of Biology, Slug Division | nomenclature. / A slug, by any other
> Case Western Reserve University | name, is still a slug by nature.
> Cleveland, Ohio 44106-7080 U.S.A. | -- apologies to Data, "Ode to • Spot"
>
That's an interesting topology. If someone is using Master/Slave principle,
he could take some of the master processing time to give voice to each
slave, like cycling thru all the nodes. He could even build an
online/offline scheme without taking down the network. Each slave could
Answer "no request to do" or "I have a job request for node number x". This
way, the master could cycle all the nodes, and if the highest node + 1 is
reached, no answer is detected, and then the master could ask "anybody
over?". Then if a node had been taking down within two other nodes, the
leftover node could answer "i'm over here". The master could rebuild the
nodes number. This way, you could add and remove any processors on the
network.
Even easier:
Each processor is fashionned in a token ring manner. But the main
difference is that every processor is a master at a time. Like if a flag
was circulating between each processors hands. Each time a processors ends
its job, it hands the flag to the next processor. When a processor is taken
down in the middle of the chain, the processor before the hole could simply
asks again "Did we forgot someone?" and then the other processors leftover
could answer "yes". Then the first processor could ask for a token
restructuration.
wow! i'm beginning to love networks :) I wish I had three or four HB :)))
cya all!!
o________________________o________o
| Remi Desrosiers \ |
| "My Youth in Arcadia" \ |
| harlock@videotron.ca \ |
O----------------------------O----O
I love Mako!! ^_^
"Y'en a pas d'problèmes!"
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Message is in Reply To:
 | | spi serial port.
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| Has anyone done any work on 'networking protocol' using the spi port on the handy board to communicate with other 6811's/handy boards/mini-boards? Any information regarding the spi for serial communications or a simple network would be appreciated. (...) (27 years ago, 27-Jun-97, to lugnet.robotics.handyboard)
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