[Tinyos-help] Getting extra bytes in CRC in TOS_Msg packet

Hello, I am sending some packets from two micaz motes to base station.The data observed using xlisten program.Some times i am getting crc value 3 bytes.Actually it should be 2 bytes according to TOS_Msg structure.Can somebody explain me this. something like following.I should get all 15 byte

[Tinyos-help] How to get timestamps in microseconds for micaz motes

Hello, We want to measure time between two events using timestamps in microseconds.(micaz motes) 1) receiving time of a radio packet 2) beep listening,by calling Mic.readToneDetector() command. how can i get the timestamps. thankyou for your assistance warm regards Umesh