20
serial COmmuniCaTiOns
When using a PXU with RS485 communications option, the PXU will support Modbus communications. Unit configuration,
as well as data interrogation, can be accomplished through Modbus communications. The PXU allows for 32 Read / Write
registers. A complete list of Modbus registers is available at the end of this document.
CRIMSON SOFTWARE
Crimson is a Windows
®
based program that allows configuration of the PXU
controller from a PC. Crimson offers standard drop-down menu commands to
make it easy to program the PXU controller, the PXU database can then be
saved in a PC file for future use. The Crimson 2.0 software is available at www.
redlion.net. An RS-485 PC card or USB to RS485 converter and cabling is
required. Prior to downloading or extracting the database, the PXU must be set
to Modbus RTU communications type. The proper communications port, baud
rate, and unit address must be configured in the Link, Options dialog and must
match the baud rate and unit address configured in the PXU serial communications
module (7-SC).
PXU CONFIGURATION USING CRIMSON
1. Install Crimson software, available for download at www.redlion.net.
2. Connect communications cable from PXU to PC.
3. Supply power to PXU.
4. Configure serial parameters as Modbus RTU (rtu), 38,400 baud, address
247.
5. Create a new file (File, New) or open an existing PXU database within
Crimson.
6. Configure Crimson 2 Link options (Link, Options) to the serial port which the
communication cable is attached (in step 2).
7. Select Update (Link, Update).
PXU FREQUENTLY USED MODBUS REGISTERS
Only frequently used registers are shown below. The entire Modbus Register Table can be found at the end of this document.
The following is an example of the necessary query and corresponding response for holding register 2. In this example register 2 is the decimal value 123.
Query: 01 03 00 01 00 01 D5 CA
Response: 01 03 02 00 7B F8 67
Notes:
1. The PXU registers can be read as holding (4x) or input (3x) registers.
2. The PXU should not be powered down while parameters are being changed. Doing so may result in an in-complete write to the non-volatile memory and produce
checksum errors.
REGISTER (4x) REGISTER NAME LOW LIMIT HIGH LIMIT
FACTORY
SETTING
ACCESS COMMENTS
1 Process Value (PV) N/A N/A N/A Read 1 = 1 Display unit
2 Active Setpoint (SP) -999 9999 0 Read/Write 1 = 1 Display unit
3 Setpoint 1 (SP1) -999 9999 0 Read/Write 1 = 1 Display unit
4 Setpoint 2 (SP2) -999 9999 0 Read/Write 1 = 1 Display unit
5 Setpoint Deviation N/A N/A N/A Read Only 1 = 1 Display unit
6 Alarm 1 Value -999 9999 100 Read/Write 1 = 1 Display unit
7 Alarm 2 Value -999 9999 200 Read/Write 1 = 1 Display unit
8 Alarm 3 Value -999 9999 300 Read/Write 1 = 1 Display unit
9 Output Power 1 0 1000 0 Read/Write 1 = 0.1%; writable when in manual mode only.
10 Output Power 2 0 1000 0 Read/Write 1 = 0.1%; writable when in manual mode only.
11 PB Proportional band (Active) 1
999(.9)° or
9999 (process)
70 Read/Write 1 = 1 Display unit
12 Integral time (Active) 0 9999 120 Read/Write 1 = 1 second
13 Derivative time (Active) 0 9999 30 Read/Write 1 = 1 second
14 Integration default (Active) 0 1000 0 Read/Write 1 = 0.1 % output power
15 PID parameter set selection 0 1 0 Read/Write 0 = PID Set 1, 1 = PID Set 2
16 Auto-Tune Start 0 1 0 Read/Write 0 = No; 1 = Yes
17 Control Mode Transfer (Auto/Manual) 0 1 0 Read/Write 0 = Automatic (PID), 1 = User (Manual Mode)
18 Controller Status 0 1 1 Read/Write 0: Stop, 1: Run
19 Setpoint Select 0 1 0 Read/Write 0=SP1, 1=SP2
20 SP Ramp Rate 0 9999 0 Read/Write 1 = 1 Display unit/minute
21 LED Status N/A N/A N/A Read Only
b0: ALM3, b1: ALM2, b2: F, b3: C, b4: ALM1,
b5: OUT2, b6:OUT1, b7: AT
22 Pushbutton Status N/A N/A N/A Read Only
b1: F2, b2: Down, b3: P, b5: F1, b6: Up, b7: D;
0 = Key pressed, 1 = Key not pressed
23 Alarm Reset 0 7 0 Write b0: Reset Alm1, b1: Reset Alm2, b3: Reset Alm3
24 Setpoint Ramping Disable 0 1 0 Read/Write 0 = Enabled, 1 = Disabled
25 Integral Action Disable 0 1 0 Read/Write 0 = Enabled, 1 = Disabled
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