| ??? 04/23/07 20:02 Read: times |
#137841 - He didn't ask for ancient or modern, just answers Responding to: ???'s previous message |
Erik Malund said:
With IIC, SPI, various serial bit-banged schemes
Today when most modern (sorry Richard) derivatives have large internal Flash and RAM, you have all port pins availble since none are 'occupied' by external memory interfacing. not to mention that there are sevaral 8 porters available. With that many port pins, there is no need for MMIO except in rare cases. Erik True enough in certain cases, but if one needs more than the puny 8KB of XRAM, and needs it to be fast, and accessible to external DMA, well, what would you recommend? I don't know about your work, but I do run into that sort of thing frequently enough that I think about it. Right now, I have a device I'm interfacing via DMA to a 128KB XRAM using bursts of ~90KB at 20 Mb/sec. This is "old-hat" to me. It wouldn't be so if it didn't come up fairly often. How would you run DMA into your internal 8KB XRAM? Aside from that, the O/P didn't ask about ancient or modern anything. He asked for an explanation of MMIO. RE |
