Tait T2000-A75, Руководство по эксплуатации, Страница: 11 / 38

November 2001 M2256-000-00-051 11
3 Transparent Mode Operation
The Transparent Mode transmission format is as follows:
The default Transparent mode Lead In Delay is set to 200 ms. If a faster data rate is required the
Lead In Delay can be reprogrammed to a minimum of 40 ms using the PROGRAM command.
Note that if the Lead In Delay is set this low, Economy mode must be disabled.
The Tail Time of 20 ms is fixed in the A75 firmware.
Transparent Mode effective data rate calculation
The Transparent mode effective data rate is dependant on the amount of data sent in one trans-
mission. The more data is sent, the better the data rate.
Example
If we assume that 1K bytes of data is sent with a Lead In Delay of 200 ms:
Time to send data m block head for each block of data
= ((( 1000 + ( 22 x 6 )) x 8 /1200 ) x 1000 = 7546 ms
Where:
1000 = bytes of data (1K bytes)
22 = (1000 bytes/46 bytes per data block) + 1 block to round up to the nearest block
= number of block heads
6 = bytes per block head (2 bytes for PR 2 bytes for SYNC + 2 bytes
for block LENGTH)
therefore:
(22 x 6) = total bytes in the block heads
8
= bits per byte
1200 = bits per second (bps) over-air standard baud
1000 = to convert bps to ms
Lead In Delay and Tail Time = 200 + 20 = 220 ms
Total time = 7546 + 220 = 7766 ms
Effective data rate = 10000 (bits) / 7766 (ms) =
1287 bps
If 1M byte of data is sent, the effective data rate goes up to 1500 bps .
Lead In
Delay
(200ms) First block
(maximum 46
bytes) . . . . . . . . nth block
(maximum 46
bytes) Tail Time
( 20ms)
Preamble Sync Length data block
(maximum
46 bytes) dummy CRC
(00)
Block Head