Campbell Scientific TX312 High Data Rate GOES Transmitter - Manual (Page 33)

TX312 Transmitter
5.2.4.1 Buffer Control
The first parameter of Edlog instruction 126 (P126) is called buffer control.
Buffer control has two purposes: 1) to determine which buffer data is written
to, and 2) if the buffer is erased before data is written. The TX312 has two
independent buffers, one for self-timed transmissions and one for random
transmissions. The self-timed buffer is treated differently than the random
buffer. After a self-timed transmission, the data is erased from the self-timed
buffer. After a random transmission, the data in the random buffer is
scheduled to be transmitted again. Random transmissions are repeated at
random intervals until P126 is used to “Clear Random Buffer” or the maximum
number of random transmissions have been met. The maximum number of
random transmissions can be set in SatCommander, default is off.
5.2.4.2 Data Format
The second parameter of P126 is used to format the data. The data is
formatted as P126 copies data from the datalogger to the transmitter.
CSI floating point binary data requires 3 bytes per data point. Data must be
low resolution. Sign and decimal location are maintained. This is an efficient
data format.
Floating point ASCII requires 7 bytes per data point. Data must be low
resolution. Sign and decimal location are maintained. Data does not need to
be converted after transmission. Data points are separated by a comma. This
is not an efficient data format, but it is convenient.
Binary, 18 bit, integer data format requires 3 bytes per data point. All data
stored in the datalogger must be in high resolution. All information right of
the decimal place is truncated. Data is transmitted as a signed, two’s
compliment, 18-bit integer. Precision can be maintained by pre and post
processing. This is an efficient data format that requires conversion and post
processing. See Appendix F for details.
RAWS 7 and fixed decimal ASCII are used to format data in a specific way.
See Appendix D for details.
5.2.4.3 P126 Result Codes
The third parameter of P126 requires an input location. In the input location,
the result of the P126 execution is stored as a result code. The result code can
be used to determine if P126 executed successfully. Under most conditions, if
P126 was not successful, a second execution of P126 will work.
To better understand the result codes, it is necessary to understand the
sequence of communication with the transmitter. Here are the steps:
1) The Datalogger CS I/O port is checked to see if the serial port is available.
If not, return code 6.
2) The transmitter is addressed and should return the STX character within
200 msec. If there is no response from the transmitter, result code 2 is
returned. If something other than the STX character is received, result
code is 3.
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