The wiki is incorrect, and I'll update it. Your observations on the datasheet are correct.
The actual CRC check in software is done after the SACK has been issued, but the hardware is intelligent enough to know not to send an ACK if the CRC failed. -David _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of renjie huang Sent: Tuesday, March 04, 2008 10:55 AM To: tinyos-help@millennium.berkeley.edu Subject: [Tinyos-help] False acknowledgments and CRC When I read following link, I have some question: http://docs.tinyos.net/index.php/CC2420_Known_Issues "False acknowledgments can get sent back for corrupted packets that are not actually received. The issue is that acknowledgements are sent before the CRC check is performed." Does it mean hardware acknowledgments are send before CRC check is performed? But from CC2420 datasheet, it seems that AUTOCRC should be also enabled when hardware acknowledgment is enabled. Following is from CC2420 data sheet: "CC2420 includes hardware support for transmitting acknowledge frames, as specified in [1]. Figure 22 shows the format of the acknowledge frame. If MDMCTRL0.AUTOACK is enabled, an acknowledge frame is transmitted for all incoming frames accepted by the address recognition with the acknowledge request flag set and a valid CRC. AUTOACK therefore does not make sense unless also ADR_DECODE and AUTOCRC are enabled. " -- Renjie
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