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Grogster

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Posted: 02:41am 23 Apr 2015

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I was playing around with some Master/Slave micromite setups tonight, and came across an error when specifying the slave address:

I2C SLAVE OPEN &B0000000,0,0,TXD,RXD
Error: Invalid 7 bit device address

MM manual page 71 states that 7-bit addresses should be in the range of 08h - 77h, or between 000 and 111 in BCD.

This gives eight possible addresses, but that may be limiting in some situations.

3-BIT ADDRESS TRUTH TABLE:

000(0)
001(1)
010(2)
011(3)
100(4)
101(5)
110(6)
111(7)

&B0000000 does not work, neither does &B1111000, but &B1010000 does, as I plopped the standard 1010 EEPROM devices group ID in front of my tinkering.

I can find nothing in the manual that tells me to stick to the 1010 EEPROM device addressing group, so can I just get some clarification here?

EDIT: Redo truth table so BCD in parenthesis mathematically match the binary notation.Edited by Grogster 2015-04-24

Smoke makes things work. When the smoke gets out, it stops!

twofingers

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Posted: 02:53am 23 Apr 2015

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Hi Grogster,

Grogster said MM manual page 71 states that 7-bit addresses should be in the range of 08h - 77h, or between 000 and 111 in BCD.

I could not find that!

But this (p 73):

Quote Another indicator that a vendor is using 8-bit addresses instead of 7-bit addresses is to check the address range.
All 7-bit addresses should be in the range of 08 to 77 (hex). If your slave address is greater than this range then probably your vendor has specified an 8-bit address.

"The range of 08 to 77 (hex)" (or 9-119 dec) is correct for 7 Bit addresses.

Best Regards
MichaelEdited by twofingers 2015-04-24

causality ≠ correlation ≠ coincidence

BobD

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Posted: 03:06am 23 Apr 2015

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Not sure what you mean by 08h to 77h or 000 to 111 in BCD.
However, the range in hex is as you said and that is 8 to 119 in decimal for 7 bit addressing. &B1111000 is out of range which is why it is invalid. It is used for 10 bit addressing.

See the attachment
2015-04-23_130513_I2C_Slave_Addressing.pdf Edited by BobD 2015-04-24

twofingers

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Posted: 03:16am 23 Apr 2015

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correction

Quote "The range of 08 to 77 (hex)" (or 9-119 dec) is correct for 7 Bit addresses.

Should be:
"The range of 08 to 77 (hex)" (or 8-119 dec) is correct for 7 Bit addresses.

causality ≠ correlation ≠ coincidence

Grogster

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Posted: 03:31pm 23 Apr 2015

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@ twofingers & BobD - Sorry, that is a typo the 000-111 thing. As you have stated, it should have been 008-119. My mistake - sorry.

Thanks very much for the PDF - that clears up many of my addressing questions, and now that I know there are some reserved address ranges as per the table on page 1 of that PDF, I can now choose any other address and it is working fine.

Thanks guys, and where did you find that PDF?Edited by Grogster 2015-04-25

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BobD

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Posted: 04:15pm 23 Apr 2015

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Grogs
There is actually a comment in the PDF as to its source. However, that source has been superseded by I2C bus Specification and User Manual rev 6 by NXP Semiconductors. See page 13 for details about addressing.

I can't be sure about this now but I think I ripped the info from that reference doc and tarted it up in MS Word then produced a PDF. I have the original in a DOCX format. The table is on page 17 of the ref document.
Bob

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