Precision Digital PD941 - Manual (Page 47)

ConsoliDator Multi-Channel Controller Instruction Manual
47
MODBUS ® SERIAL COMMUNICATION
The controller is equipped with serial communication capability as a standard feature. Baud
Rate, Parity, Modbus ID (Address) and Transmit Delay are entered in the General
Functions box, which appears in the main setup menu. The baud rate and parity selected
must match the settings for all other devices on the network. Modbus ID must be unique so
it will not interfere with other devices.
ConsoliDators support the following Modbus control functions:
Command Name Description
03 Read Holding Register Read multiple bytes from holding registers.
05 Write Single Coil Set single coil value control
06 Write Single Register Set single value into specified holding register.
16 Write Multiple Registers Set multiple values into specified holding registers.
Note: To save data to non-volatile memory after changing the contents of holding register(s) use the
Write Single Coil command [command code 05] to “ON” at address 64251.
To control the relays via MODBUS you would use the Write Single Coil command
[command code 05] and send either the “ON” or “OFF” to the appropriate alarm relay (1-9).
The ConsoliDator can also work as a "MODBUS Display" by setting the desired analog
input channel to the "FIXED" type and then over MODBUS change the "K-Factor/Modbus
Display" value for the corresponding channel. This input type is transparent to the rest of
the functions of the unit (i.e. relays, etc...). The value, once the EEPROM save command is
sent to the unit, is also maintained in EEPROM after the next power cycle.
Modbus Register Tables
Table 1. Analog Output Channels Register Addresses
Address (offset from 40000)
Description Data Type Ch. 1 Ch. 2 Ch. 3* Ch. 4*
801 819 837 855
4 mA Value Floating Point
802 820 838 856
803 821 839 857
20 mA Value Floating Point
804 822 840 858
805 823 841 859
Set point Value Floating Point
806 824 842 860
807 825 843 861
PID KP Floating Point
808 826 844 862
809 827 845 863
PID KI Floating Point
810 828 846 864
811 829 847 865
PID KD Floating Point
812 830 848 866
813 831 849 867
PID Output Value Floating Point
814 832 850 868
815 833 851 869 PID Cycle Time Integer
816 834 852 870 Output Type Byte
817 835 853 871 Input Ch. Byte
818 836 854 872 PID Direction Byte
*Channels 3-4 only apply to ConsoliDator 4 (PD940 & PD941) models.