Ruud Baltissen wrote: > Hallo Martijn, > > > Does anyone have the *electrical* specifications of the IEEE488 bus? > > I have to dig up the exact info at home. But AFAIK you should recon with > about 3 Kohm for every line. . ^^^^^ Shouldn't that read 'device' ? > This means 15 mA is sufficient enough to drive 8 peripherals. Okay, that's enough for the time being. It's not completely according to the official standard, but I can live with that :) > I assume you intend to use every portpin in bidirectional mode. Yes. Saves a *lot* of I/O pins. It would be Real Nice (TM) I could squeeze it into just one 8751 and nothing else save some glue. > I thought I may have some 8751's laying around, but I'm not able to program > them. Programming a 8751 isn't really difficult. I have the specifications floating somewhere on my desk at Philips. Interested in a copy? > Could these be of some help for you? Well, I use a 89c51RD+ for my 8051 development. That thing has 64K flash, which can be programmed over an RS232 connection. Rather convenient. It's a shame that this cute chip isn't available at electronic part resellers. (Mail-order companies like Conrad have it, though). > Questions: > - Is it going to be bi-directional? (My Tripod lacks this feature :( ) Well, it's a bit too early to make any sensible remark about this :) It would be nice, though. I haven't completely figured out how I want things to work exactly; I don't want to make it a 'transparant proxy', for that would slow things down tremendously. Suppose you have a PET, a diskdrive (4040, 8050, whatever), this converter and a 1541. It would be a shame if the connection between the PET and the 4040 would be slowed down because of the 1541.. > - As you only need about 20 lines, 4 are left over. What a an extra RS232 > port? Hmm. I don't really follow you here. A 8751 has 4 I/O ports (thus 32 IO lines). However, I think that the end result will probably consist of a 8031 (the ROMless version of a 8751) with an external EPROM. In that case, you loose 2 ports because of the address/databus which sits at ports 0 and 2. (It may be possible to reclaim a few IO lines though, I don't think that you'll need the full address range of 64K) Regarding an extra RS232 port: The 8751 has a built-in RS232 port; if you want to add a *second* one, you'll end up bit-banging such a thing. I'm not quite sure if that's possible, since the IEC-bus has to be bit-banged as well. (hmm. Maybe not; maybe I can abuse the UART for that..) Anyway; thanks for the info :) -- Martijn van Buul - Pino@dohd.org - http://www.stack.nl/~martijnb/ Geek code: G-- - Visit OuterSpace: mud.stack.nl 3333 Kees J. Bot: The sum of CPU power and user brain power is a constant. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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