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07/28/09 17:26
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 		 #167969 - re: Max 8 I2C addresses
Responding to: ???'s previous message
Maarten Brock said:
Where did you find that limitation? Surely I2C can address 128 devices.


Many I2C devices hardwire at least some of the slave address bits and allow the user to select only two or three. PCA9555 lets you select only A2, A1 and A0, and A[6:3] are fixed at 0100. So while I2C lets you address 128 slaves, you can only have eight 9555s on one bus.

-a


List of 109 messages in thread
TopicAuthorDate
switchover from 8048 to 8031            01/01/70 00:00      
   P4-P7 whereabouts            01/01/70 00:00      
      This might be a bit trickier than you think ...            01/01/70 00:00      
         interfacing 8243 to uprocessor            01/01/70 00:00      
   Replacing one dinosaur with another?            01/01/70 00:00      
   Maybe you should reconsider the system configuration            01/01/70 00:00      
   8048 -> 8051            01/01/70 00:00      
      if you buy a SILabs kit ...            01/01/70 00:00      
         Beware of 'C'-only systems ...            01/01/70 00:00      
            Pardon??!            01/01/70 00:00      
               I have to believe their tech support guys ...            01/01/70 00:00      
                  The SILabs 'tools' are KEIL            01/01/70 00:00      
                     My point, exactly!            01/01/70 00:00      
                        WHO states that he has to use Keil            01/01/70 00:00      
                           There's probably good reason for that!            01/01/70 00:00      
                              the KEY word            01/01/70 00:00      
                                 You can't evaluate with something that's not complete            01/01/70 00:00      
                                    But they obviously can't give away the complete product            01/01/70 00:00      
                                       migration of 8243 expender            01/01/70 00:00      
                                          what specifically does not work?            01/01/70 00:00      
                                       Of course not!            01/01/70 00:00      
                                          Agree with you there!            01/01/70 00:00      
                                          On the subject of cars ...            01/01/70 00:00      
                                             When I feel like it            01/01/70 00:00      
            male cow manure            01/01/70 00:00      
               The tools SiLabs wants you to use ...            01/01/70 00:00      
                  the old familar tune and singing it off key            01/01/70 00:00      
                     Lots of C code to fill 2kB or 4kB            01/01/70 00:00      
                        and how will that help the O/P?            01/01/70 00:00      
                        maybe if the lines are....            01/01/70 00:00      
                           Don't you worry            01/01/70 00:00      
                              It was a kind of joke.            01/01/70 00:00      
                        Illustrated here            01/01/70 00:00      
                  2K of binaries for just a few dozen lines of 'C'            01/01/70 00:00      
                     perhaps, but the O/P didn't say he wants to use 'C'            01/01/70 00:00      
                        You were the one who raised it!            01/01/70 00:00      
                           True enough, but ...            01/01/70 00:00      
                              read the Keil manual            01/01/70 00:00      
                           I don't believe that's the case            01/01/70 00:00      
                              Yes, it was definitely you.            01/01/70 00:00      
                                 Emulation possible            01/01/70 00:00      
                                    why not emulate 8048 in 8051            01/01/70 00:00      
                                       Interesting idea, but ...            01/01/70 00:00      
                                          how to 8243            01/01/70 00:00      
                                             It could be quite straightforward            01/01/70 00:00      
                                                it could be....            01/01/70 00:00      
                                             how to 8243            01/01/70 00:00      
                                                You really should open a museum!            01/01/70 00:00      
                                                   You really.....            01/01/70 00:00      
                                       conv51            01/01/70 00:00      
                                 Yep ... you're right ...            01/01/70 00:00      
                                    SiLabs parts            01/01/70 00:00      
                                       It's not at all clear what the problem is            01/01/70 00:00      
                                    I know that you live in the past            01/01/70 00:00      
                                       it's all about the timing ... and the support            01/01/70 00:00      
                                          If it matters, then you shouldn't be asking            01/01/70 00:00      
                                          living in the past, you would not know of ...            01/01/70 00:00      
                                       quality of support            01/01/70 00:00      
                              "Most coders"            01/01/70 00:00      
                                 do you really have any evidence            01/01/70 00:00      
                                    You clearly haven't though about it!            01/01/70 00:00      
                                       which is the correct procedure            01/01/70 00:00      
                                          Not so ridiculous ...            01/01/70 00:00      
                                             when I discuss a, you invariably bring up b            01/01/70 00:00      
                                    assembler code            01/01/70 00:00      
                                       C and assembler are complements            01/01/70 00:00      
                  That's meaningless, Richard            01/01/70 00:00      
                     It's not pointless, Andy            01/01/70 00:00      
                        2kB of code space is quite a lot for evaluation            01/01/70 00:00      
                           One could answer this in a number of ways ...            01/01/70 00:00      
                              I think I know why Richard keeps arguing against C ...            01/01/70 00:00      
                                 In that case, where's the benefit?            01/01/70 00:00      
      It is unclear...            01/01/70 00:00      
         8048 to 8051 migration            01/01/70 00:00      
            240 i/o pins is an awful lot            01/01/70 00:00      
               Many alternatives            01/01/70 00:00      
               I doubt he's using 240 I/O pins            01/01/70 00:00      
                  240 pins i/o            01/01/70 00:00      
                     Have you considered Programmable Logic?            01/01/70 00:00      
                     What will you do when those i8243's are exhausted?            01/01/70 00:00      
                        old 8243 equipment            01/01/70 00:00      
                           It's entirely up to you            01/01/70 00:00      
                           Max 8 addresses on I2C?            01/01/70 00:00      
                              wouldn't it be wise to start thinking about this right now?            01/01/70 00:00      
                                 wouldn't it be wise...            01/01/70 00:00      
                              I2C configuration for 240 I/Os            01/01/70 00:00      
                                 PCA9501            01/01/70 00:00      
                                    Decentalized options ?            01/01/70 00:00      
                                       I would definitely look at multiple controllers            01/01/70 00:00      
                              max 8 adresses...            01/01/70 00:00      
                                 SPI often cheap compared to I2C            01/01/70 00:00      
                                    not necessarily true            01/01/70 00:00      
                                       not nessesarily true            01/01/70 00:00      
                                          WHY?            01/01/70 00:00      
                                             51 derivative            01/01/70 00:00      
                                                IIC chips            01/01/70 00:00      
                                          cheaper            01/01/70 00:00      
                                             cheaper            01/01/70 00:00      
                                                FAQ            01/01/70 00:00      
                                    shift register            01/01/70 00:00      
                              re: Max 8 I2C addresses            01/01/70 00:00      
                                 two options            01/01/70 00:00      
                           NXP has a line of "bus splitters"            01/01/70 00:00      
            Still unclear [edited]            01/01/70 00:00      
               8048 to 8051 migration            01/01/70 00:00      
                  AT89S8253            01/01/70 00:00      
                  AT89S8253            01/01/70 00:00      
                     Sorry... duplicated post!!            01/01/70 00:00      
            8048 vs 89S52 DIP40 may fit but different pinout            01/01/70 00:00      

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