Xylem System 5000 User Manual - Manual (Page 67)

Outputs
65
PDT
Platform Description Table.
Note: Each DCP will have a PDT defined on a computer system at NOAA. If the table is not completely defined, then
when data is retrieved the error message “PDT RECORD IS NOT COMPLETE,” will appear. Part of this table describes
the Radio manufacture and model number.
Preamble
This is a carrier signal sent to the satellite before any data is sent. Only 100 baud transmissions
can send a Long Preamble.
Preamble Type Short Preamble Long Preamble
Total Preamble Time 0.98 seconds 7.3 seconds
SHEF Codes
A two character code that describes the DCP message data type. Common SHEF codes include:
HG = Height, River Stage
TA = Temperature, Air
VB = Voltage, Battery
Transmission Window
The scheduled time interval at which a DCP can transmit data in the Self-Timed mode. This is
normally a one-minute window for 100 baud transmissions. GOES Radios using the higher baud
rates may be assigned a shorter window.
UDT
User Description Table.
Understanding Binary Data
The Self-Timed pseudo-binary transmission and all Random transmission formats use a 6-bit per
byte pseudo binary format. The following shows the byte format:
1 Byte Value:
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
Parity Always 1 DATA 5 DATA 4 DATA 4 DATA 2 DATA 1 DATA 0
3 Byte Value:
Byte 3 Byte 2 Byte 1
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
p
1 D
17 D
16 D
15 D
14 D
13 D
12 P 1 D
11 D
10 D
9 D
8 D
7 D
6 P 1 D
5
D
4 D
3 D
2 D
1 D
0