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Chapter 4: Network Topologies
S212: Max Expected Packet Size—(Set only on Master). S212 is the maximum packet size the remote units can send to the
master, therefore defining the duration of the data slot for the remote units. The remote S112 register must be equal to or less
than the value of the master’s S212 register.
S168: Sniffer Mode—(Filter mode). This option can be used to set up Fast TDMA mode so that remotes can receive data from
other remotes, not only from the master. This information could be used in systems where units could benefit from information
collected by others.
Entering the TDMA Table:
ATT? View the entire registered TDMA table.
ATTn=UA Enter a Slave’s Unit Address (UA) into the TDMA table. n = the position in the table. Use 0 to terminate the list.
ATTn? View a specific entry in the TDMA table.
Limitations:
a. Remote diagnostics is not supported because packets sizes vary. Only local diagnostics is supported in this mode.
b. Repeaters are not supported.
Factory default settings AT&F18 (Master) and AT&F19 (Slaves)
AT&F18 and AT&F19 provide default settings for the Master (AT&F18) and a default slave (AT&F19). These default settings can be
overwritten if needed. The values set by using these commands are as follows. Additionally, a default TDMA table is populated as
listed.
Master Fast TDMA (AT&F18)
ATS244=2
// Fast TDMA mode
ATS112=235
// Master’s maximum packet size.
ATS212=130
// Maximum packet size
ATS184=150
// Data time to live in 10ms, e.g. 1.5s
ATS232=10
// Incoming user data limit, e.g. 10 buffers
Slave Fast TDMA (AT&F19)
ATS244=2
// Fast TDMA mode
ATS112=130
// Slaves’ maximum packet size
ATS184=150
// Data time to live in 10ms, e.g. 1s
ATS232=10
// Incoming user data limit, e.g. 10 buffers
ATS248=10
// Synchronization time-out in seconds, e.g. 10s
If register S168 is 1 or 2 (default 0), slave receives data from everyone in the network (sniffer).
