AD9528: which registers are buffered? (and need io_update)

HI,

I believe only the registers 0x0000 and 0x0001 are live registers. All the other registers are buffered. 

"is there some configuration registers that do not need IO_UPDATE?"

All configuration registers require IO Update. See the initialization procedure from page 42 in rev G data sheet. One writes all the registers and then executes IO Update.

You can do the following to verify if a register is buffered or not:

- let's consider register 0x300.

- in the eval software, read the register with register debug window(View, Debug). In my case, the value is 0x00.

- I'm writing it with value 0x38. I can read it back as 0x38.

-I'm setting register 0x0001 with value 0x20, so when you execute a read operation, you read the buffer.

-I'm reading register 0x300, which means I read the buffer of the register 0x300. I read 0x38, so the register is buffered.

Petre

Thank you pminc48 

I would say that register IO_UPDATE (0x000F) is also live.

By the way, your sequence of reads and writes is not so clear to me. Using the debug window,

• write reg0x001 with 0x00 (default value) "reads values currently applied to the internal logic of the device."
• read reg0x300: 0x40 (in my case)
• write reg0x300 with 0x00
• read reg0x300: 0x40 because the value previously written is not yet applied
• write reg0x001 with 0x20 "reads buffered values that take effect on the next assertion of IO_UPDATE"
• read reg0x300: 0x00
• write reg0x001 with 0x00
• read reg0x300: 0x40
• write ref0x00f with 0x01 IO_UPDATE
• now reg0x300 always read 0x00 whatever the value of reg0x001

Anyway, would have been nice to have in the datasheet the list of buffered registers.