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Original question:
CDCE913: I2C byte access to odd address
Replies: 4
Views: 72
Part Number: CDCE913
Hi, I was trying to read registers from CDCE913 and values returned seemed wierd to me :
So I went on the forum and I vagly read the thread "CDCE913: I2C byte access to odd address" where I saw that register address where different than mines, like this :
So I tried to add what seemed to be an offset of 0x80, and then I've got less wierd values :
Could you, please, tell me if the last values readed are the registers that I'm looking for ? (Generic Configuration Registers)
If so i'd like to change the slave address but I'd rather be sur it's the right register before writting anything
Regards,
Marine CHESSA
(P.S. : for now the device work porperly I just need to get the slave adress 0x65 free for an other device)
Pictures didn't follow, please find it in the file attachedCDCE913_valuesreadeddocx.docx
In reply to Marine Dino:
Hi Marine,
I'm not sure if I understood your question correctly. But first, last two bits of I2C address are programmable:
Second, I2C read/write instructions are in the datasheet:
For example, if you want to read back the value of register R5, you first write the device slave address, then a "0" for write, then write the address of R5 (0000 0101). Then repeated start sign, device slave address, a "1" for read, and the next byte you read back will be the register value.
Regards,Hao
Clock and Timing Systems & Applications
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In reply to Hao Z:
Hi Hao,
I have a I2C bus, which is functionnal (I can read and write others devices on the bus)
I'm also able to read CDCE913 registers.
I know that I can change the slave address and that's what I'm aiming for.
BUT when I read the register "0x01" the device answers "0x07" ==> ok why not .... (by curiosity I also read others register as 0x02,0x03,...,0x06 answers were always "0x07" ==> wierd)
As it was wierd I've search on the forum, and I saw that someone added some "offset" to registers adresses, instead of adressing "0x01" (=0b0000 00001) he was adressing "0x81" (=0b1000 0001).
(https://e2e.ti.com/support/clock-and-timing/f/48/p/858572/3176365#3176365
So I tried to use it to read my registers, I had the following answers
read register 0x81 ==> 0x01
read register 0x82 ==> 0xb4
read register 0x83 ==> 0x01
read register 0x84 ==> 0x02
read register 0x85 ==> 0x50
read register 0x86 ==> 0x0e
Those answers seems more legit than "0x07"
So my question is : When I send a "read" on the register address "0x81" am I reading the "Generic Configuration Register 01h" ??Then can I write to this register with the confidence that it will do what I want ? And not affect the device fonction in an unwanted way ?
Thank's by advanceMarine
Sorry for the late response. I believe that the "1" in bit 7 of 0b1000 0001 stands for read; and 0 is for write.
To check if you wrote something correctly, you can choose a non-readonly register and see if you can read back what you write.