YSI 6500 Environmental Process Monitor - Manual (Page 48)

Proper Use and Care of the 6500
Section 5
The following table shows the register areas defined in the 6500:
Address Read/Write
Description
1-128 Unused
129-143 Read/Write Parameter type
The PLC must write to this area to tell the 6500 what
parameters it wants. Up to 15 parameters can be written here.
After the last parameter the PLC must write a “0”. For
example to instruct the 6500 to provide depth in feet followed
by temp in C the following should be written:
129: 23 (code for depth in feet)
130: 1 (code for temp in C)
131: 0 (tells the 6500 that this is the end of the list)
144-256 Unused
257-271 Read only Parameter status
The PLC can read back the values in these registers to check
the status of the parameters. The value in register 257
corresponds to the parameter type in register 129 and so on.
The meaning of the returned value is:
0 – The parameter is enabled in the sonde and actively
functioning.
1 – The parameter type is set to 0 (code for end of list).
2 – The parameter requested is not currently available in the
sonde.
272-384 Unused
385-414 Read only IEEE floating point parameter data
This is the actual parameter data in floating point form. Two
registers are used for each value to make up the 32 bits
required for a 4 byte IEEE floating point number. The value
in register pair 385:386 corresponds to the parameter type in
register 129 and so on.
It is highly recommended that this be used rather than the
scaled integer format. There several reasons for this:
• It’s easier to use since the numbers aren’t scaled. For
example a temp C value of 22.34 would be transmitted as
is, rather than as a converted value such as 7234.
• There is no implied range of values for a parameter.
Using scaled values forces a limit to the range of possible
values that a given parameter can take on.
• The maximum resolution of the data can be transferred.
415-640 Unused
YSI Incorporated 6500 Environmental Process Monitor 45