Discussion in "General help Guidance and Discussion" started by    scorcho    Sep 29, 2006.
Fri Sep 29 2006, 09:13 am
#1
Hi,

I have a project where I'm considering interfacing a serial EEPROM, a Toshiba MCU and another IC via the I2C bus. The MCU communicates with the serial EEPROM to receive some data, which it will then do some processing on, and feed it to the other IC.

The IC actually expects data to come from a serial EEPROM, so the MCU acts as one. As such, the IC must be configured as master with the MCU as slave, with the MCU having a specific address as defined by the IC. However, since the MCU is first getting data from the serial EEPROM, it's probably going to also act as Master to the slave EEPROM. The data transfers between the 3 chips happen one after the other, and do not overlap.

I'm wondering if it's possible to do with just 1 I2C bus, since my MCU only supports 1?

Thanks!
Fri Sep 29 2006, 12:16 pm
#2
hi,
well i didnt get actually what is going on in your project.. it will be easy to understand if you can make a small block diagram.
what i got from your explanation is.. the serial EEPROM is in between two MCUs. just remember that.. I2C bus is not limited to one device on a one bus.. ok! you can have multi-slave or multi-master configuration. on a single bus..
so.. you can have EEPROM and the other MCU on the same bus.. no need to have another bus.. both can communicate over the same bus...
if possible please try to provide a small block diagram to explain it more easily.
Fri Sep 29 2006, 01:31 pm
#3
Here's a small block diagram in ASCII

--------     ---------         ------
|Serial|/___\|Toshiba|SL____\MS| IC |
|EEPROM|\   /|  MCU  |      /  |    |
--------     ---------         ------


Now I know that I2C is a bus so it shouldn't be a P2P connection like how I drew it, but I'm trying to show that the MCU sits between the EEPROM and the IC, and that the EEPROM never directly talks to the IC. Also:
1) The IC expects the MCU to be slave(SL).
2) The MCU communicates with the EEPROM, then with the IC. These do not overlap and happen one after the other
3) The EEPROM-MCU is bidirectional while the MCU-IC is unidirectional(MCU sends data to IC)
Fri Sep 29 2006, 02:12 pm
#4
I2C never overlaps the data..
coz every device on the bus has an address. so nothing overlaps unless and until the address is same and that is not possible.
you can have everything on same bus.. no need to make it saparate.
so the diagram will be something like this
 ________          ________ 
|Serial    | /___\\ |Toshiba|
|EEPROM| \\ |  / |  MCU  |
|________|    |    |_______|
                 \\|/
          _________
         |     IC     |
         |________|

i have used the same configuration.. with a RTC, EEPROM, and MCU and works great.

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