Dwyer PPM - Manual (Page 31)

MPM, APM, PPM, & LTI Series Modbus ® Register Tables Serial Communication
Page 31
Notes
Note 1. The Register numbers and addresses follow the Modbus format:
 3xxxx are for Input Registers and are read – only.
 4xxxx are for Holding Registers and are read/write.
Although there are no specific 3x Registers, all 4x Registers are mirrored
into 3x register space, and are therefore capable of being read by
Modbus function 04 (Read Input Registers). All data addresses in
Modbus messages are referenced to zero (0), while Register addresses
are referenced to one (1). For example, Register 40100 is sent in the
Modbus message as 0x0063 (100 - 1 = 99 ≡ 63 hex). If two addresses
are shown separated by a “ – ”, they form a register pair to make the
parameter into a 4-byte (32 bit) value.
Note 2. Limits or Range: Writing a value that is outside the parameters range will
force it to be limited to the closest value within the range. For example, if
the range is -1.99 to +1.99 and the value sent is 3.21, the value used is
1.99. Likewise for the lower side of the range. Exceptions are noted in
the comments.
Note 3. Data Types:
Data format is highest byte first.
Word = 16 bit
Integer = -32768 to 32767
Unsigned integer = 0 to 65535
Long = -2,147,483,648 to 2,147,483,647
Float = IEEE floating point format, 4 bytes
Integers data: The values represent the number without regard to the
decimal point. The decimal point setting can be found in Holding
Register 40102.
For example, if the number 1234.56 is displayed, a read of both 40021 –
40022 together will return 1 – 23456 (0x0001 – 0xE240). Register 40102
will contain 2 (0x0002) to indicate a decimal point setting of two places
to the right of the decimal point. A floating point version of the displayed
number, with the decimal point included, is also available by accessing
register 40001 – 40002.
Example (register values are shown in hexadecimal):
Process value
displayed
Registers
40001 – 40002
Register
40021
Register
40022
Register
40102
123.456 42F6 – E979 0001 E240 0003
1234.56 449A – 51EC 0001 E240 0002
12345.6 4640 – E666 0001 E240 0001
-1234.5 C49A – 5000 FFFF CFC7 0001
Note 4. A read of the Password register will return 0x000000 if the meter is
unlocked, otherwise it will return 0xFFFFFF to indicate a locked meter.
To unlock, the correct lock number must be written, which will then clear
the lock number to 0x000000. If the wrong lock number is written, the
reply will return 0xFFFFFF. If the correct lock number is written, the reply
will be 0x000000. An unlocked meter can be locked by writing any non –
zero value up to 0x999999.
Note 5. Remote scaling procedure:
a. Write the desired values for the display, Display 1 & 2, for
the active input type. The active input type is selected using
the Input Selection register 40101 and
Table 1 .
b. Write the desired values for the input, Input 1 & 2, for the
active input type.
c. Write to the remote scaling register for the active input
type.
Warning!
The scaling process takes the input values and converts them
to A/D counts. Therefore, do NOT execute a remote scaling
register write without first writing the display and input registers.
In a similar vein, don’t write to the mA registers and then
execute a remote scale command for the volts input.
Warning!
Always allow the meter and the signal input circuitry to warm –
up at least 20 minutes prior to calibrations. The scaling process
takes the input values in mA or volts and converts them to A/D
counts. Therefore, do NOT execute a remote scaling register
write without first writing the display and input registers. In a
similar vein, don’t write to the mA (volts) registers and then
execute a remote scale command for the volts (mA) input.