# So DOUT buffer of the Coordinator Xbee may contain RF data with incorrect checksum also??

**URL:** <https://forums.digi.com/t/so-dout-buffer-of-the-coordinator-xbee-may-contain-rf-data-with-incorrect-checksum-also/15874>\
**Category:** XBee - 802.15.4\
**Tags:** dout-buffer, rf-check-sum, xbee\
**Created:** [December 2, 2015, 1:08am UTC](https://forums.digi.com/t/so-dout-buffer-of-the-coordinator-xbee-may-contain-rf-data-with-incorrect-checksum-also/15874 "2015-12-02T01:08:18Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Ajith](https://avatars.discourse-cdn.com/v4/letter/a/bcef8e/32.png) [@Ajith](https://forums.digi.com/u/Ajith)\
**Post date:** [December 2, 2015, 1:08am UTC](https://forums.digi.com/t/so-dout-buffer-of-the-coordinator-xbee-may-contain-rf-data-with-incorrect-checksum-also/15874/1 "2015-12-02T01:08:18Z")

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Or is the RF check sum test performed before storing in DOUT buffer? Say while sending data from RF RX buffer to DOUT buffer.

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**Author:** ![mvut](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.digi.com/mvut/32/31_2.png) [@mvut](https://forums.digi.com/u/mvut)\
**Post date:** [December 2, 2015, 8:40am UTC](https://forums.digi.com/t/so-dout-buffer-of-the-coordinator-xbee-may-contain-rf-data-with-incorrect-checksum-also/15874/2 "2015-12-02T08:40:02Z")

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Yes. The radio will only send out the UART valid frames. For that matter, valid data is not provided to the radios UART from the RF buffer until it has been verified as a valid packet.

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**Author:** ![Ajith](https://avatars.discourse-cdn.com/v4/letter/a/bcef8e/32.png) [@Ajith](https://forums.digi.com/u/Ajith)\
**Post date:** [December 2, 2015, 9:18am UTC](https://forums.digi.com/t/so-dout-buffer-of-the-coordinator-xbee-may-contain-rf-data-with-incorrect-checksum-also/15874/3 "2015-12-02T09:18:00Z")

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Could you please elaborate your answer in terms of RF RX buffer and DOUT buffer as mentioned in Xbee series 1 datasheet.

Data goes from Xbee Receiver to RF RX buffer. Then from there to DOUT buffer. Then to DOUT pin.

So it is clear that Valid Data through DOUT pin has been Verified as Valid packet.

And you have said that RF data with incorrect check-sum can be present in the buffer. But which buffer is it the RF RX buffer or DOUT buffer??

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**Author:** ![mvut](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.digi.com/mvut/32/31_2.png) [@mvut](https://forums.digi.com/u/mvut)\
**Post date:** [December 2, 2015, 11:28am UTC](https://forums.digi.com/t/so-dout-buffer-of-the-coordinator-xbee-may-contain-rf-data-with-incorrect-checksum-also/15874/4 "2015-12-02T11:28:02Z")

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Let me explain it this way:

Data is received on the antenna port and passed to the RF Receive buffer.

The RF Receive buffer then verifies that the data is for this module or not and if it passes the Checksum. If it does, it is then past to the UART Data out buffer to be sent out the UART. If the data does not pass the checksum, the data is discarded. If the packet is found not to be for this module, it will discard the packet.

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**Author:** ![Ajith](https://avatars.discourse-cdn.com/v4/letter/a/bcef8e/32.png) [@Ajith](https://forums.digi.com/u/Ajith)\
**Post date:** [December 2, 2015, 4:17pm UTC](https://forums.digi.com/t/so-dout-buffer-of-the-coordinator-xbee-may-contain-rf-data-with-incorrect-checksum-also/15874/5 "2015-12-02T16:17:37Z")

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Thanks a lot. Its much more clear to me now.