Hallo allemaal, This mail answers several mails in one. >From Bogax: > Assuming your talking about 16 bit transfers(?), > see "handshaking" under "6526 functional description" in the PRG. > > "Handshaking on 16-bit data transfers (using both PORT A and PORT B) > is possible by always reading or writing PORT A first." This taken from http://www.funet.fi/pub/cbm/documents/chipdata/6522-VIA.txt written by Frank: Port A consists of eight lines which can be individually programmed to act as inputs or outputs under control of a Data Direction Register A. The polarity of output pins is controlled by an Output Register and input data may be latched into an internal register under control of the CA1 line. If you read a 6526 port then you get the data which is there at the moment of reading. With the 6522 you can latch the data. This feature is used in the 1541. The data on a floppy is read bit by bit and parallellised using a 74LS164 or 166 (don't have SCHs here to check). Just for 3 or 4 MICRO-seconds the valid byte is present at the outputs. This is too short for a processor to notice and to react. So the data has to be latched in a temporary memory. The signal to perform this latching is also used to notify the processor and is connected to the SO-input of the 6502. The point is that IMHO the 6526 has NOT this latch feature onboard. Why do I need this feature? When reading a _16_ bits databus, a C= can only read 8 bits a time. So I develloped a trick in 1989 (?) using to 74ALS573's. I later used this trick with my IDE-interface: http://home.hccnet.nl/g.baltissen/ide-c64.gif Two 573's mean 40 pins to solder. A 6522 has 40 holes as well PLUS some extra features like an extra 8 bits wide port. For David: as you now probably understand, the 5622 was meant for the data, not for the address. For Ethan: > Linux supports hundreds of netcards. literally. All of linux is open > source. Enough said ;) I must admit that I forgot about that. > Hook it up the same way the 6526 is hooked up ;) Unfortunally this is not possible :( The reason is technically: (if my memory serves me well) the 6522 already expects a valid address on the rising edge of CLK2. And we all (should) know that the VIC-II controls the lower half of CLK2. The trick is to delay this rising edge so long as needed to give the 6510 some time to output a vilid address. But I'm not familiar with the exact timing and I know Frank is. Groetjes, Ruud http://Ruud.C64.org ----- Original Message ----- From: <firstname.lastname@example.org> To: c64-maillist <email@example.com> Sent: Wednesday, April 04, 2001 5:28 AM Subject: RE: Article PC-card > > > On Tue, 3 Apr 101 firstname.lastname@example.org wrote: > > > Hallo Ethan, > > > > > but there are drivers for IDE, network cards of various flavors (NE2000, > > > 3c503, 3c509 and 80x3, primarily), serial ports, printer ports and a few > > > odd devices under AmigaDOS and UNIX. > > > > Are the sources of the drivers available? > > Linux supports hundreds of netcards. literally. All of linux is open > source. Enough said ;) > > > > and use a 64Kb AUTOCONFIG block rather than a 1Mb block for those A2000 > > > users who want a full 8Mb of RAM in their systems). > > > > I'm not familiar enough with the Amiga to understand this "64Kb AUTOCONFIG". > > It's a _working_ plug'n'play system. To be honest, I"m surprised Miccrosoft > didnt steal it like it did nearly everything else it has. > > > > If this discussion ever results in any hardware being designed, I'd love > > > to build one. > > > > The Amiga supports 16 bit, the C64 and almost all other C='s don't > > Writing the above lines, I got the idea to use a 6522 for the upper 8 > > databits. This is it has this feature being able to latch data. This > > feature is used in the 1541 (and maybe other drives as well). > > or a 74574 octal latch. The 6522 is a little overboard, dont you think? > > > > > Questions: > > - I studied the Prog. Ref. Guide but couldn't find this feature so I may > > asume that it is not on the 6526. Can anybody confirm, please? > > - I know it is possible to connect a 6522 to a C64 and Frank wrote an > > article about it, but cannot find it :( Can anybody tell me where to find > > it, please? > > Hook it up the same way the 6526 is hooked up ;) > > - > This message was sent through the cbm-hackers mailing list. > To unsubscribe: echo unsubscribe | mail email@example.com. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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