Z8530 (was Re: Navtel 9460 Protocol Analyzer info?)

On 4/14/05, Scott Stevens <chenmel at earthlink.net> wrote: I should look at that code sometime, mostly out of curiosity. . If I'm not wrong (from my cursory glance over the My recollection of it with COMBOARDs is that the most important thing is not to feed the chip too fast from the bus side. The second most important thing is to understand what register you are accessing and calling it up properly. We were using the 4MHz parts with an 8MHz 68000. Our design was basic - a single PAL to handle address selection and R/W sorts of things, and a simple interrupt design. No DMA. We were only dealing with speeds up to 64kbps sync serial, so the lack of DMA didn't kill us. The 4MHz parts just about did. The code that thwacked on the serial chip took a while to refine to a simple set of elements that worked reliably. One trick I remember was that we *always* made sure to have some minimum number of cycles between picking and internal register, and accessing that register. The most ordinary technque was a fixed number of NOPs after writing to the initial register. I don't know anything about how the SPARCs or the Mac interfaced to the Z8530, but our design was particularly inexpensive, but it was fast enough to talk to the required interfaces. Even so, there _were_ tips and tricks we'd learned the hard way. As I said, I should have a look at the NetBSD code and compare tricks. It's still a nice chip, especially if one wants to talk sync or async multi-character internal buffer (Z85230?), but it's much less common than the original. -ethan