| ??? 03/26/06 00:02 Read: times |
#113092 - RE: Just exactly who cares about it? Responding to: ???'s previous message |
Richard Erlacher said:
If he's the rank beginner that he says he is, he needs, first of all, to learn how silly it is to sacrifice two ports on his MCU in order to gain the three ports on the 8255.
RE Well Richard, i need much more than 3 IO ports, 7 to be exact. Richard Erlacher said:
He then needs to learn a few things about the general notion of what an 8-bit MCU can appropriately be used for and lastly how silly it is to use a mid-range MCU like he's wanting to use together with a three-generations-obsolete part like his 8255.
RE Richard, that's right but even i was confused when i saw a Swiss firm selling a board to one of my clients for his textile weaving machine. Believe it or not, it had almost all these same components, except for the 8259. And, although the board was a replacement part, the machine itself was designed and sold to my client in 2001. Moreover, in another application, i had to install a centralised Home-automation system for another client. He purchased the HomeVision system (you can find the website by searching for HomeVision in Google). This system has a DS80320 chip (ok, i know this is an advanced chip but even this has been marked as nearly obsolete by Dallas), 2 8255s, and a lot of legacy components. You can even see trhe board and components on the website of this system. Richard Erlacher said:
Now, there are applications that the 8255 can handle, but there are better ways, particularly if he doesn't intend to attach the 8255 as a memory-mapped peripheral, which, of course, he can't do if he pushes up the speed of his MCU beyond the typically half-microsecond access time of his 8255.
RE Please suggest how the 8255s can be used in another manner with the 8052 clones. Richard Erlacher said:
He also needs to learn that the PIC (interrupt controlle) doesnt' marry up with the 805x types nearly so well as with the 8080 for which it was designed.
RE True, but this was just for experimentation purposes. The 8259A is supposed to work with INTA lines of the 8088 / 8086, and hencei have used a port line to signal the INTA pulses to the 8259A. Couldnt think of any other interrupt expanding IC. After all, i am just a begenniner. Richard Erlacher said:
The 8279 is not at all designed for use with the 805x, particularly since he's not going to use the keyboard or the display for which that part was intended. He's got the intention of putting on an LCD. They didn't even have those when the 82xx series was designed.
RE Well, i intend to use the 8279 with a keyboard and LED-digit based display, while i have mapped a separate port of the LCD on the board. Richard Erlacher said:
Let him build his one-of-a-kind project, and let him learn what he can learn from it. Eventually he'll arrive at the conclusion that there are reasons why these parts are scarce and no longer made. When he gets to the point at which he realizes that he needs to use parts intended to be used together, and that they should be parts of the same generation in order to allow seamless integration, he'll have learned something.
RE Thanks, bro. I know this is a one-of-a-kind project which would have been a very ambitious one back in the '80s but well, this is also my first big project by-hand. I have worked with embedded 386 boards, but these boards were all pre-developed SBCs to which i attached extra IOs or functions as the need be so. But building something from scratch is the first time for me. And i was limited by resources, client needs and demands and lack of availability of advanced parts here in this geographic region, not to mention that the production quantities are very low (lesse than 100 pcs at most). Richard Erlacher said:
You're a smart guy, Kai, and expert in your field, but I think you're solving the wrong problem here.
RE Ditto. |
