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DL-40JANUS-DCA/DCV manual (d0114)
Page 7
The Modbus/RS-485 communication settings sub-menu allows
you to set the following parameters:
a) Baud Rate – this is the baud rate of the RS-485 serial communi-
cation between the meter (slave) and Modbus master. Options are
9600 (default, meter shows “96”) and 19200 (meter shows “192”).
b) Address – this is the meter’s Modbus address on the RS-485
loop. Typically, RS-485 limits the number of devices on the loop to
32, but the DL-40 supports the full Modbus address range of 1-247.
Address 1 is the default value.
c) Parity – this is the parity setting for the RS-485 serial commu-
nication between the meter (slave) and Modbus master. Options
are: None (display shows “0”; Odd (display shows “1”); Even
(default, display shows “2”).
The meter’s response time to a read command from the master is
40-45msec (typically 42msec). The response time for a write com-
mand is 70-75msec (typically 72msec). This is due to the module
having to communicate to the meter’s core firmware to complete
the desired command. Exception responses are handled directly
by the module and typically have a response time of 3msec.
Modbus RTU & RS-485 Communication Settings
The DL-40 Modbus communication module supports the following
Modbus commands:
a) Read Holding Register (0x03)
b) Write Single Register (0x06)
Modbus addresses for DL-40JANUS registers are shown on
the next page
The following are some things to note about particular registers:
a) Modicon address 40001 RELAY has the bit values for Sp3 &
Sp4 and LED3 & LED4 reversed. There is an historical reason
for this, and we have chosen to maintain backward compatibili-
ty in case customer’s want to send their meters in for a Modbus
upgrade (at a nominal fee).
b) Modicon addresses 40002 INP, 40026 PEAK, 40027 VALY,
40029 ZERO, 40029 SPAN return a 2 byte hexadecimal value
of the meter’s display (in counts) and does not include the deci-
mal point. If you need the decimal value with decimal point, you
will need to read the register, convert it to decimal, read 40024
(see below) to determine decimal location, then combine the
two. Display counts are in Two’s Complement notation.
a. Hex values for 0 to 9999 are 0x0000 to 0x270F.
b. Hex values for -1 to -1999 are 0xFFFF to 0xF831.
c. Over-range is indicated by a returned value of 9999
(0x270F).
d. Under-range is indicated by a returned value of -1999
(0xF831).
c) In order for Sp3 and Sp4 set point settings to work, the DL-40
must have the optional Output Carrier Board installed (P/N
SA-DL/OM-CB).
d) All Delay on Make (DoM), Delay on Break (DoB) and Hysteresis
values are in units of whole seconds.
e) Modicon address 40023 RLYMOD uses the following values
to set the relay activation mode (letter sequence is SP1, SP2,
SP3, SP4):
a. 0 for HHHH
b. 1 for HLHL
c. 2 for LHLH
d. 3 for LLLL
e. H means relay is energized if input is equal to or
exceeds setpoint; L means relay is energized if input
is less than setpoint.
f. Note that the meter will not show the last two letters if
the Output Carrier Board option is not installed.
f) Modicon address 40023 DP uses the following values to set the
display decimal point location:
a. 0 for XXXX (none)
b. 1 for XXXX.
c. 2 for XXX.X
d. 3 for XX.XX
e. 4 for X.XXX
g) Modicon address 40025 BRIGHT must be a value between 1
(most dim) to 4 (most bright).
h) Modicon addresses 40028 and 40029 will have different mean-
ings depending on the Auto calibration or Manual rescaling
operational selection (see Auto Calibration Mode or Manual
Rescaling Mode above). These are explained in the register
table below.
i) Modicon addresses 40030 IZERO and 40031 ISPAN return
hexadecimal values related to the Auto Mode calibration of the
meter. They do not necessarily match expected values due vari-
ations and tolerances in the measurement circuit components,
e.g., calibrating with a value of zero volts for the ZERO value
may return a value of 0xFFFE (-2). These registers have no
meaning in Manual Rescaling Mode).
Modbus RTU Implementation
