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???
07/25/09 09:30
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 		 #167867 - I2C configuration for 240 I/Os
Responding to: ???'s previous message
The classic IO expander with I2C bus is the PCF8574. It provides 8 IO pins and an interrupt.
The two versions PCF8574 and PCF8574A have different address on the I2C bus
(7bit) PCF8574 20h-27h
(7bit) PCF8574A 38h-3Fh
By this in mind on a I2C bus you can setup 8chips PCF8574 = 64 IO and 8chips PCF8574A = 64 IO TOTAL=128 IO
If you setup a second I2C bus you can have another 128 IO TOTAL=256 IO that fulfills the 240 IO requirement.
http://www.nxp.com/acrobat_download/datasheets/PCA8574_PCA8574A_2.pdf



The two I2C busses may set up on any 8051 derivative by software or to choose a derivative with two physical I2C busses.
Another option is to use a 16bit IO expander like PCF8575.
More like the PCA9505/9506 provide 40 bit parallel I/O for I2C bus organized in 5 banks of 8 I/Os
http://www.nxp.com/acrobat_download/datasheets/PCA9505_9506_3.pdf

Other considerations as FPGA or CPLD have already discussed on previous posts.

K.L.Angelis

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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