Technical data

Technical Datasheet
&
User’s Manual
Narrowband multi-channel data radio modem
LinkWiser™-S400M Rev. 2.1
Cellution Inc.
#317, NKIC, 48-84 Honguen-1dong, Seodaemun-gu, Seoul, Korea Zip: 120-760
Enquiries: [e-mail]
/ [e-mail]
Voice: [phone] / Fax: [phone]
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12-5-3 UART Timing in Tx
You MUST configure the Serial Link Time Out value depending on DEPENDING ON YOUR SERIAL
BAUD RRATE.
EX) If your serial baud rate is 9600bps, we recommend over 1ms of the Serial Link Time Out value.
Thus, you can get a result same as the above Figure2.
9600bits/second = 9600bps, then 960bytes/second because start bit & stop bit should be added.
1byte time interval in the UART section at 9600bps is around 1.042ms. And data processing time from
the LinkWiser is required. That is less than around 0.8ms. Thus, over 2ms of the Serial Link Time Out
value is recommended.
A (ms) > = 1,000 (1 sec = 1,000 milli sec.) / Serial Baud Rate (bps) / 10 (start bit + 8 user bits + stop
bit) + 0.8ms
If we apply the calculation to various UART baud rates,
Over 9ms of the Serial Link Time Out value is recommended in 1200bps
Over 4ms of the Serial Link Time Out value is recommended in 2400bps
Over 3ms of the Serial Link Time Out value is recommended in 4800bps
Over 2ms of the Serial Link Time Out value is recommended in 9600bps
Over 1ms of the Serial Link Time Out value is recommended in 19200bps
12-5-4 Air Timing
Apart from the above Serial Link Time Out value, developers & integrators MUST recognize &
calculate how long the LinkWiser occupy a frequency to complete transmitting the USER DATA
from host(s).
First of all, you have to understand that the LinkWiser doesn’t send the USER DATA as is. The
LinkWiser re-packetizes the USER DATA to transmit into the air.
Normally 51 bytes of packet overhead in case of transparent networking topology & 53 bytes of
packet overhead in case of address networking topology are required to add on USER DATA.
Thus, the calculation is as follows;
1 Byte Time Interval (B) = 1,000 (1 sec = 1,000 milli sec.) / AIR RATE (bps) / 8 (8 bits = 1 byte)
Ex) 1.67ms = 1,000 / 4,800bps / 8
But, LinkWiser adds some headers and footers on existing USER DATA. Thus, [ USER DATA (bytes) +
51 (Transparent) or 53 (Address) ] + 2ms (Margin) = Total Air Time (ms)
Ex) If air rate is 4800bps & USER DATA is 50 bytes in transparent mode,
1.67 (B) * [ 50 (USER DATA) + 51 (Overhead, Transparent) ] + 2 (Margin) = around 170.67ms
12-5-5 UART Timing in Rx
There is no time interval.
12-5-6 Conclusion (TOTAL TIME CONSUMING)
C (ms) = A (ms) + B * [ USER DATA (bytes) + 51 (Transparent) or 53 (Address) ] + 2 (Margin)
Ex) If air rate is 4800bps & UART baud rate is 9600bps & USER DATA is 50 bytes in transparent
mode,
2 (A) + 1.67 (B) * [ 50 (USER DATA) + 51 (Overhead, Transparent) ] + 2 (Margin) = around 172.67ms
There is 112.67ms of actual overhead latency comparing to 60ms in wire connection in case of