© Microhard Systems Inc.
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5.0 Network Topologies
To calculate the duration of the entire Fast TDMA Frame:
For the link rate 172kbps:
T_tdma_table(N_entries) = 2.3076 + 0.0684 * N_entries;
T_data_packet(N_bytes) = 1.9327 + 0.0673 * N_bytes;
T_total = T_tdma T_data_packet_Master* N_M
T_data_packet_Slave* N_Slaves, where N_M N_Slaves = N_entries
For Example: You have a system with 5 remotes and 1 master as seen below:
Master
UA = 1
SL2
UA=2
SL5
UA=5
SL11
UA=11
SL7
UA=7
SL22
UA=22
The Master collects data from Remote 2, 11, 5, 7, and 22. Remote 5 contains GPS data, you
want this data updated more frequently than the data from the other units. You also need to
send correction data three times per frame to ensure accurate readings. Your TDMA table
may look something like:
TDMA Table
UA,
// Position
1,
// 1
5,
// 2
2,
// 3
11,
// 4
1,
// 5
5,
// 6
7,
// 7
22,
// 8
1,
// 9
5,
// 10
The Max packet size of the remotes, S212 on
master = 100 bytes
The Max Packet size of the Masters data to the
remotes, S112 on master = 200 bytes
Using the formula given above:
T_tdma_table(10) = 2.3076 + (0.0684 * 10) = 2.9916
T_data_packet_Master(200) = 1.9327 + (0.0673 * 200) = 15.3927
T_data_packet_Slave(100) = 1.9327 + (0.0673 * 100) = 8.6627
T_total = 2.9916 + 15.3927*3 + 8.6627*7
T_total = 2.9916 + 46.1781 + 60.6389
T_total = 109.8086
We find that the entire TDMA frame will take just under 110 ms
