Den Sat, 04 Aug 2018 08:24:05 +0200 skrev André Fachat <afachat@gmx.de>: > > > Am 4. August 2018 8:14:03 AM schrieb Jim Brain <brain@jbrain.com>: > > > On this portion of the 2031LP schematic: > > > > ftp://www.zimmers.net/pub/cbm/schematics/drives/old/2031/page-12r.gif > > > > The DC pin for the 75161 is not shown. Does anyone know what it is > > connected to? > > Here's the schematic for the 1541 IEEE488 refit > http://www.6502.org/users/andre/cbmhw/ieee488/index.html that is > basically the same hardware as the 2031. I wounder how hard it would be to change the rom to use PB4 instead of PB0 for ATN ack (and therefore also move another signal as all pins are used)? PB4 is the pin used for ATN ack on a 1541 and in 1541 mode the pinout needs to be the default for all turbo loaders, copy protection stuff and similar to work. But I don't know of any copy protection or "turbo load" software for 2031LP, so there might not be any incompatibles. By swapping PB4 and PB0 the same ATN trap circuit could be used both in serial and in IEEE-488 mode. Btw it would be nice to get rid of the 75160/75161 and replace them with something else. Even though they are still available, they seem to not be that common. For example TME (one of the larger sellers in Europe) only has 75161 and not 75160 unless I'm mistaken. For someone ordering a bunch and selling a bunch of ready made conversion kits, like Jim seems to be planning, this might not be a problem. But for everyone who like me would rather just build a one-off thing it would be nice to be able to use whatever is more easily obtained or even something that usually already exists in an electronics hobby component box. It seems like the 74AC/ACT family can sink/source 24mA, while the 75160/75161 can sink/source 48mA. Every other 74xx family is worse at drive and/or sink. But the 74AC/ACT family might not be a good choice as the cmos input protection diodes will load the bus when the unit containing AC/ACT circuits is powered off. So in practice the 74xx family could probably be ruled out, unless several bipolar IC's is piggy backed. What does the IEEE-488 standard actually spec? And what is the actual electrical data on Commodore hardware? It seems like the 75160/75161 loads the bus with up to 3,2mA when the bus is low, and up to 2,5mA when the bus is high. For something to be really usable in a PET/CBM setup, I think a reasonable minimum system would be 3-4 devices. For example a PET, an 8080/8250 drive and a 1541 converted to 2031LP, and room for one more device. As I understand it, a 74F245 should be able to drive six 75160/75161 inputs. Ref: http://www.ti.com/lit/sg/sdyu001ab/sdyu001ab.pdf -- (\_/) Copy the bunny to your mails to help (O.o) him achieve world domination. (> <) Come join the dark side. /_|_\ We have cookies.Received on 2018-08-05 20:00:05
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