eeprom address

Tumbler

Hi

I want to use a second eeprom with the address pins A0= 3,3v, A1=gnd and A2=gnd
and John's i2c demo.

I think i have to change this line in the DAT section, but i don't know what this line means.

EE = $A0 | (%001 << 1)

Can somebody help me with this?
thx

MacTuxLin

Another way to see this is:

EE = %101000000 OR %00000010
EE = %10100010
EE = $A2

Tumbler

And how to change this line for my setup?
A0= 3,3v, A1=gnd and A2=gnd

MacTuxLin

Tumbler wrote: »

A0= 3,3v, A1=gnd and A2=gnd

This means this EEPROM's address A0. Your 2nd EEPROM is A2? If so, A2 should be pull-up.

Duane Degn

MacTuxLin wrote: »

This means this EEPROM's address A0. Your 2nd EEPROM is A2? If so, A2 should be pull-up.

I'm not sure what you mean by an address of "A2". The address pins are used to assign the EEPROM one of eight possible addresses.

The address of the EEPROM has this format.

p1010AAAX (I have to use a "p" instead of the percent sign because the forum software has a fit with the percent sign.)

The "AAA" part corresponds to which address pins are pulled high. Pin A2 is the most signifiicant of these bits.

"X" indicates if the command is to read or write.

The original EEPROM on the Prop has all address pins connected to ground so the address is "p1010000X".

If pin A0 is pulled high, then the address is "p1010001X" (or setting the last bit to zero initially, you'd use "p10100010").

The first four bits of the address "p1010" is the device address. Since the following three bits can be changed by setting one or more of the address pins high, it's possible to have eight EEPROMs on the same I2C bus.

This address information is covered pretty well in the datasheet. Microchip's datasheet has this information in section 5.0 "Device Addressing" (page 8).

blittled

It looks like EEPROMS can be addressed by using HEX A0 and by using the A0-A2 lines. If you want a second EEPROM tie line A0 high. Since the EEPROMS are I2C the address must be shifted left 1 i.e. EE := A0 | (Address (From A0-A2 lines) << 1). I2C uses bit 0 to determine if it reading or writing to an EEPROM. So if you tie A0 high you use EE = $A0 | (%001 << 1)

Tumbler

Okay, got it now. Thx all for the help.

Tumbler

Below a part of the jm_i2c_demo:

{{ 
                                 3.3v
                                     
                24LC512        │  │  │
          ┌─────────────────┐  │     4k7      
       ┌──┤1 A0        VCC 8├──┘  │  │     
       ┣──┤2 A1         WP 7├──┐  │  │ 
       ┣──┤3 A2        SCL 6├──│──┻──│── SCL pin   
       ┣──┤4 GND       SDA 5├──│─────┻── SDA pin             
       │  └─────────────────┘  │
                              

       
   Be careful using this program with the boot EEPROM -- corrupting the program/data
   space can lead to expected results.  If boot EEPROM is 64K (24LC512) addresses from
   $8000 to $FFFF are safe (not used by Propeller).
       
}}

and line 51:
EE = $A0 | (p001 << 1) ' device address

That's for an eeprom with the A0 pin high, not the boot eeprom.
A typo?

Duane Degn

Tumbler wrote: »

EE = $A0 | (p001 << 1) ' device address

That's for an eeprom with the A0 pin high,

The above sets EE to $A2, which would be the address for an EEPROM with the A0 pin high.

With all address pins low (as with the boot EEPROM), the address should be $A0.

WBA Consulting

I had much of the same confusion when creating my Secondary EEPROM Bootloader. Check out this thread to see if it helps at all:

http://forums.parallax.com/showthread.php?129700

JonnyMac

That demo was a bit long in the tooth and I have made several improvements to my I2C object. The updated code and demo is posted in ObEx

-- http://obex.parallax.com/objects/528/ (link corrected)

You probably understand by now that the slave id for an I2C exchange is formatted thusly

-- TTTTAAAM

...where TTTT is the device type (%1010 for EEPROMs and similar devices), AAA is the 3-bit address for the device (if addressable; RTCs, for example, are not and fixed at %000), and M is the mode bit (0 for write, 1 for read).

g3cwi

Jon

Your link needs to be this:

http://obex.parallax.com/objects/528/

The one you posted only works for the submitter of the object.

Cheers

Richard

Tumbler

Thx for the update John

JonnyMac

Thanks for the catch; link is corrected.