Murata Electronics North America DNT500FP Manuel D’Utilisation
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DNT900 - 11/05/08
structure. As an example, consider a TDMA Mode 2 or 3 system operating at 500 kb/s. Up to 10 regis-
tered remotes need to be accommodated. A BaseSlotSize of 138 bytes is needed, and each remote
needs enough slot time to support a RemoteSlotSize of 64 bytes. The minimum hop duration needed to
support this configuration is:
tered remotes need to be accommodated. A BaseSlotSize of 138 bytes is needed, and each remote
needs enough slot time to support a RemoteSlotSize of 64 bytes. The minimum hop duration needed to
support this configuration is:
= 2.388 + 10*0.970 + 0.0160*(138 + 10*64)
= 12.088 + 0.0160*778
= 24.536 ms
= 12.088 + 0.0160*778
= 24.536 ms
The closest programmable hop duration is 24.550 ms.
In all TDMA modes, the base station operating system will commandeer one byte from the BaseSlotSize
allocation for each registered remote to send ACKs to the remotes. The BaseSlotSize and MinPacket-
Length
allocation for each registered remote to send ACKs to the remotes. The BaseSlotSize and MinPacket-
Length
should be sized accordingly.
2.9 Serial Port Operation
DNT500 networks are often used for wireless communication of serial data. The DNT500 supports serial
baud rates from 1.2 to 460.8 kb/s. Listed in the table below are the supported data rates and their related
byte data rates and byte transmission times for an 8N1 serial port configuration:
baud rates from 1.2 to 460.8 kb/s. Listed in the table below are the supported data rates and their related
byte data rates and byte transmission times for an 8N1 serial port configuration:
Baud Rate kb/s
Byte Data Rate kB/s
Byte Transmission Time ms
1.2
0.12
8.3333
2.4
0.24
4.1667
4.8
0.48
2.0833
9.6
0.96
1.0417
19.2
1.92
0.5208
38.4
3.84
0.2604
115.2
11.52
0.0868
230.4
23.04
0.0434
460.8
46.08
0.0217
Table 2.9.1
To support continuous full-duplex serial port data flow, an RF data rate much higher than the serial port
baud rate is required for FHSS. Radios transmissions are half duplex, and there are overheads related to
hopping frequencies, assembling packets from the serial port data stream, transmitting them, sending
ACK’s to confirm error-free reception, and occasional transmission retries when errors occur.
baud rate is required for FHSS. Radios transmissions are half duplex, and there are overheads related to
hopping frequencies, assembling packets from the serial port data stream, transmitting them, sending
ACK’s to confirm error-free reception, and occasional transmission retries when errors occur.
For example, consider a CSMA Mode 0 transparent data system operating at 500 kb/s with the Bas-
eSlotSize
eSlotSize
parameter set to 133 bytes (128 bytes net after the five byte allocation for sending ACKs) and
the RemoteSlotSize parameters set to 128 bytes. The minimum hop duration needed to efficiently support
this configuration is:
this configuration is:
= 2.388 + 1*0.970 + 0.0160*(133 +1*128)
= 3.358 + 0.01 60*261
= 7.534 ms