Searching \ for '%I2c Different Speeds%' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: techref.massmind.org/techref/i2cs.htm?key=i2c
Search entire site for: 'I2c Different Speeds'.

_Sub string match.
PICList Thread
'[PIC]: I2c Different Speeds'
2001\04\13@095716 by Ronald Cotton

flavicon
face
I have 2 PICs, 16f877(20Mhz) and a 16f874(4Mhz).  I have configured the
16f874 as the Master and the 877 as the slave.
Will I have a problem with communications if the crystals are different?

Thanks


Ronald Cotton

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2001\04\13@103410 by D Lloyd

flavicon
face
part 1 873 bytes content-type:text/plain; charset=us-ascii
Hi,

No, if you are using the hardware interfaces, because I2C is synchronous.

Dan




(Embedded     Ronald Cotton <spam_OUTrcottonTakeThisOuTspamCOMPRISCORP.COM>TakeThisOuTspamMITVMA.MIT.EDU>> image moved   13/04/2001 14:59
to file:
pic12488.pcx)





Please respond to pic microcontroller discussion list
     <
.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent by:  pic microcontroller discussion list <PICLISTspamKILLspamMITVMA.MIT.EDU>


To:   .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
cc:
Subject:  [PIC]: I2c Different Speeds

Security Level:?         Internal


I have 2 PICs, 16f877(20Mhz) and a 16f874(4Mhz).  I have configured the
16f874 as the Master and the 877 as the slave.
Will I have a problem with communications if the crystals are different?

Thanks


Ronald Cotton

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics






part 2 165 bytes content-type:application/octet-stream; (decode)

part 3 144 bytes
--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2001\04\13@130650 by Drew Vassallo

picon face
>No, if you are using the hardware interfaces, because I2C is synchronous.

This should be true.  And if you're bit-banging the data (software), you
just have to make sure that your timing is correct.  Assuming you abide by
the specifications of the I2C protocol, you should have no problems.

--Andrew
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2001\04\14@041554 by Peter Tiang

flavicon
face
   Huh..?? Not sure about the PIC I2C hardware interface..
   but I2C is NOT synchronous.

   You can slow down I2C comm by holding SCL low (as
   a slave) until you are ready to give the bit data.
   That's why the requirement for an open drain
   bus.

   In fact you can run close to 0 Hz this way as
   I2C specification never specify a timeout for
   the bit handshake.

   SMBus specification, which is a variation of I2C
   added a timeout. But this is understandable
   as SMBus is adapted for managing system devices
   on PC platform.

   The only time an I2C slave have to worry about
   timing is the detection of the I2C start condition,
   which is dependent on the I2C master.

   The last I check, the worst case is at 400kHz or
   2.5us between the SDA going low follow by SCL going low.

   So if you use some external logic to detect the
   start condition (and generate a interrupt signal),
   and a uC that can service an interrupt (and output
   SCL low) within 2.5us, you can run a software
   bit-banged I2C slave on that uC.

Cheers,
Peter Tiang

========================================================

{Original Message removed}

2001\04\16@090548 by Olin Lathrop

face picon face
> I have 2 PICs, 16f877(20Mhz) and a 16f874(4Mhz).  I have configured the
> 16f874 as the Master and the 877 as the slave.
> Will I have a problem with communications if the crystals are different?

No.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, EraseMEolinspam_OUTspamTakeThisOuTembedinc.com, http://www.embedinc.com

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestspamspam_OUTmitvma.mit.edu


More... (looser matching)
- Last day of these posts
- In 2001 , 2002 only
- Today
- New search...