In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Coriolis wrote:

[quote="DigitalDj"]
Thanks Paul for the drawings and thanks to everyone contributing!
 

I am kind of new to these chips and to address them this way, i am also new to Sx programming!

 

Paul,

I have some questions on the drawings!

 

Drawing 1

1. The first drawing just has the address lines coming from the SX and i would still have to tell the (8) LM4970's address pins to go low or high to address them?

 

2. Since the LM4970's have address pins does that mean that all (8) Lm4970's can run off of the same I2C buss and then when i want to address each chip i just set the address pin of that chip?

 

 

Drawing 2

1. Are all (8) of the LM4970's using the same buss in this drawing?

 

2. Would i only be able to address one chip at a time by multiplexing?

 

3. If i can use the same I2C buss for all (8) LM4970's could i just use the SX without the mulitplexing chip for addressing the address pins of the LM4970's? 

I guess if i wanted to use more LM4970's say 16 multiplexing would be the way to go!

 

Drawing 3

1. I don't understand what's going on here with the CD4052, i need some explaination as to how this works.

 

 

Since i want to control this circuit from the USB port of the computer will that change any of these circuit ideas. The reason i want to control this circuit from the computer is it gives me more versatility. Also can i get a circuit to convert USB to I2C like the circuit from Parallax for USB to serial?

 

Sorry for all the questions!

Thanks!

Kevin

 

 
[/quote]Figure A) There are no address lines in A, the LM4970 has a single address bit, since this can be set to either a 0 or a 1 that allows a maximum of 2 4970s per traditional I2C bus. Since you have 8 4970s to connect to, that requires 4 traditional I2C busses, this is what is being illustrated in the drawing. The address is set by tieing the address pin one of the 4970 on each bus to ground (Vss), and the other 4970's address pin to Vdd. The first one will have the address 0 and the second will have an address of 1. The addresses are fixed and do not change.
 

Figure B) Yes all 4970s are tied to the same bus. The 74LS138 in B is technically a decoder, what it does is take a 3 bit value and drives 1 of 8 outputs low according to the three bit value. The other outputs are high, meaning the 4970 tied to that output will have the address 0, and all the others have an address of 1, this way one is singled out so you can access it. Your only ever going to address one at a time anyways so this setup works. The essence of this setup is being able to set the address of 8 4970s using only 3 pins on the SX.

 

Figure C) The CD4052 is a true dual-channel 4-way multiplexor, its operation is equivalent to a DP4T switch (dual pole, 4 way throw), IOW two switches which have four postions and the two switches are set to the same position. So these are used to switch a single I2C bus on the SX side to one of 4 I2C busses that contain the LM4970s, the addresses of the LM4970s are set the same as in Figure A.

 

If you want further explanation of what Geuther and Peter are talking about ask, and one of us will explain.

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