RFDATATECH URT-500, Руководство по установке, монтажу, эксплуатации и программированию

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7.3.1 RECEIVE TO TRANSMIT SWITCHING TIME
When using the internal modem the action that initiates transmission can be either receipt of a character
at the serial port or the operation of RTS. These examples use the first mode. The radio does nothing
until the stop bit of the first character for transmission has been received, the transmitter is then started:
The time delay between receipt of the stop bit for the first character to be transmitted at the transmitting
radio and output of the start bit of that character at the receiving radio is the sum of the values ttxon,
tlid, trbyte, and tmdel shown in the diagram above. Values for these parameters are indicated below:
TABLE A: Timing values for duplex and simplex modes are as follows:
symbol Description Semi-
duplex simplex
ttxon Time from external action to commencing transmission 9ms 9ms
tlid Duration of synchronisation transmission (lead in delay) Table B Table B
trbyte Duration of 1 byte at radio signal baud rate Table C Table C
tmdel Modem decode latency Table D Table D
TABLE B: The lead in delay is a programmable parameter but minimum values dependant on baud rate
must be adhered to. However, in a scanning system with the base station on continuous transmit the
base station lead in delay can be set for Zero (thereby saving valuable time) as the internal outstation
modems will always be synchronised.
Baud 150 300 600 1200 2400 4800 9600
Min tlid 80ms 60ms 40ms 40ms 40ms 20ms 30ms
TABLE C: The duration of a byte at the radio baud rate is dependant upon the data format employed,
the table below assumes a format of one start bit, 8 data bits, no parity and 1 stop bit, i.e. a total of 10
bits per character. If another format is used the appropriate correction must be made.
Baud 150 300 600 1200 2400 4800 9600
trbyte 66.7ms 33.3ms 16.7ms 8.3ms 4.17ms 2.08ms 1.04ms
TABLE D: The modem decode latency takes into account delays introduced by hardware and software
filters. The total delay is baud rate dependant:
Baud 150 300 600 1200 2400 4800 9600
tmdel 6.9ms 3.5ms 1.7ms 1.3ms 1ms 1ms 1ms
7.3.2 MESSAGE DURATION
The time taken to transmit a message can be simply derived by multiplying the number of characters in
a message by the values given in table C making any appropriate corrections for data format. The
exception is 9600 baud where extra synchronisation sent during the message must be taken into
account, 8 synchronisation bits lasting a total of 0.833ms are sent after every eighth message character.
URT500 Manual Page 25 of 42 Rev. C – 6 August 2008