STI Engineering rfi-9256, User Manual

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Operation
RFI-9256 Radio Modem User Manual Page 32 of 109
2. Each individual slave can only hear the master unit, while the master can hear all the slaves. This
means that when a master is communicating with multiple slaves there is no guarantee which slave
the RSSI value refers two, in fact it is most likely to be an average of all slaves. In order to counteract
this effect a special link margin test is provided on the master unit. The link margin test will take
control of the communications link and determine the exact RSSI that the master is receiving from a
particular slave. This is covered in Appendix B.6 on page 83.
RF COMMUNICATIONS STATISTICS
The RFI-9256 provides a number of communications statistics that can be used to debug a RFI-9256 system.
These parameters are shown in Table 9.
Statistic Description
Frame count The total number of frames that have passed while the radio has been operating.
Empty frames The number of frames that have been received but contained no user data.
Good packets The number of good packets received.
Bad packets The number of bad packets received.
Lost packets The number of packets that have been lost.
Retries The number of retries or retransmissions this unit has used while transmitting.
Good headers
The number of good header packets received. Header packets contain
synchronisation and control information.
Bad headers The number of bad header packets received.
Lost frame lock
The number of times this unit has lost lock. A loss of lock occurs on a slave when it
can no longer hear the synchronisation messages from the master.
Low RSSI
The number of times the RSSI level has been at or below the nominal sensitivity of
the radio while receiving.
Data Recv The number of user data bytes received.
Data Sent The number of user data bytes transmitted.
Rx Overflows
The number of times received data has been discarded due to there be no free frame
buffers.
Rx Overruns The number of times data has been lost due to internal radio errors.
Tx Overflows
The number of times an attempt has been made to obtain a frame buffer for
transmission, and there have been no free frame buffers.
Busy Waits
The number of times the slave radio has had data to transmit, but has been unable to
do so due to communications between the master unit and another slave radio.
Table 9: RF communications statistics