Embedded Communications Systems RMX232, User Manual

A receiving radio modem will only accept a data packet whose hop count is zero.  It is 
therefore essential that the correct hop count be specified in the modem configuration 
for the number of expected repeater hops. 

With 

rptmode

 being set to 

ALL

, the repeater will retransmit all packets regardless of 

the site address, provided the hop count for that packet is greater than or equal to 1. 

Diagnosing Network Problems Using Ping Test 

The radio modems have a built in test feature allowing the user to not only check that 
the remote unit is operating, but to also check that there are no other radio modem 
pairs using the same unit and site address. 

Under normal operation data communications is between two radio modems with 
identical unit and site addresses. If however, when setting up an additional radio 
modem pair, you are not sure of what other unit addresses are in use within a 
particular site code, then the ping function can assist in determining unused unit 
addresses. 

Only one radio modem is required to be in command configuration mode in order to 
execute the ping function. When the ping command is executed, without parameters, it 
sends out four successive ping requests using the current unit address and site code. 
After each ping request the radio modem will wait for approximately 250 milliseconds 
for a response from any remote device that matches the ping requests unit address 
and site code. 

Upon receiving a ping acknowledgement from any radio modem that is powered up 
and listening, the remote modem’s details are displayed to the user. The details 
reported to the user from the remote unit include, the baud rate setting, the serial 
number, the number of repeater hops taken and the time taken for each reply. 

Assuming that another radio modem pair are operating within radio range and using 
the same unit address and site code, the results from the ping request will show the 
details from those devices. It is then possible, using the returned serial numbers, to 
identify the other radio modem pairs. 

If a unit address is specified to the ping command, then this unit address is used for 
the ping along with the current site code. It is therefore possible to ping all 16 
addresses in a given site by just specifying the unit address with the ping command. 

Note that a remote radio modem will not respond to a ping request if it is not powered 
up or is in the power save mode (ie; DTR has put the radio modem into a power down 
state). 

Performing Site Reliability Tests Using Radar Test 

The radio modems support a function that can be used for both site testing and range 
testing the radio modems. 

The radar test, once executed, sends out continuous requests to a remote addressed 
radio modem at a predetermined rate. The remote radio modem must reply to these 
requests within a certain time frame before that particular request is considered to 
have failed. 

The displayed results from the radar test indicate the rate of successful 
acknowledgements received over the last 100 transmitted requests sent. It also counts 
the number of failed requests (up to 65535, before wrapping around to zero). 

User’s Guide 

Modem Operation Explained 4-10