TCA9536: Is it possible to overwrite unused bits in registers?

Zach Kimble

Part Number: TCA9536
Other Parts Discussed in Thread: PCA9536

Hello,

I have noticed that when I write to registers 0x01, 0x02, and 0x03, it does not seem like the first 4 bits are being overwritten. Just the second 4 bits are modified. The unmodified bits are labeled "not used" in the datasheet.

Is this behavior expected or should I be able to overwrite the unused bits? PCA9536 allows me to overwrite the unused bits so I am seeing different readback values when I compare the two devices.

Please let me know if I can provide any additional information.

Thank you!

Best regards,

Zach Kimble

over 2 years ago

+1 Tyler Townsend over 2 years ago

TI__Mastermind 40613 points

Hi Zach,

Whether the first 4 unmodified bits are overwritten, or unable to be overwritten will not affect the state machine of the device. There might be a difference in the way we structured the internal registers between the PCA and TCA versions of this device, but it will not change the way the device operates in a overall system.

Regards,

Tyler

0 Zach Kimble over 2 years ago in reply to Tyler Townsend

TI__Intellectual 1770 points

Thank you Tyler! That makes sense.

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TCA9536: Is it possible to overwrite unused bits in registers?