ModbusRTU Master
Comms Port
Description Each Modbus RTU Master will have one Comms Port function block which provides global serial port configuration, control, and monitoring.
Availability
  • Available only in the dw1xx series products
  • Requires library: System & I/O
  • Requires: Generic ModbusRTU Master Unisolated EIA-485 (option -13) or Generic ModbusRTU Master Isolated EIA-485 (option -12)
  • Singleton function block
  • Firmware versions 0x1030 and later
savvy-SFD Graphic modbusPort
Graphic with Parameters modbusPort

Parameters

Comms Speed Internal Parameter, Read-write, Enumerated (signed 16-bit integer)

The communications rate for the serial connection in bits per second (b/s) or kilobits per second (kb/s). The Comms Speed can be set to typical values from 300 b/s to 115.2 kb/s.

For proper operation, the Comms Speed parameter MUST match the slave device's settings.

High-speed comms requires careful engineering of the cable, connections, termination, etc.


0 = 300 b/s
1 = 600 b/s
2 = 1200 b/s
3 = 2400 b/s
4 = 4800 b/s
5 = 7200 b/s
6 = 9600 b/s
7 = 14.4 kb/s
8 = 19.2 kb/s
9 = 28.8 kb/s
10 = 38.4 kb/s
11 = 57.6 kb/s
12 = 76.8 kb/s
13 = 115.2 kb/s
Comms Configuration Internal Parameter, Read-write, Enumerated (signed 16-bit integer)

The character framing for the Modbus RTU serial connection in the format Data Bits-Parity-Stop Bits.
Character framing is specified as:
  • Data Bits - Fixed at 8 data bits.
  • Parity - Selectable as N (None), O (Odd), E (Even).
  • Stop Bits - Selectable as 1, or 2.

0 = 8-N-1
1 = 8-O-1
2 = 8-E-1
3 = 8-N-2
Actual Polling Period Internal Parameter, Read-only, Analog (signed 16-bit integer)
0 ms to 32767 ms

The time required to complete a poll of all parameters acquired via the serial connection.

The Actual Polling Period is directly affected by:

  • The Comms Speed setting.
  • The number of parameters polled.
  • The number of communications errors.
  • The number of communications timeouts.
  • The Comms Sleep Time.

32767 = >30s
Comms Timeout Internal Parameter, Read-write, Analog (signed 16-bit integer)
0 ms to 30000 ms

The timeout sets the time the Modbus master is to wait for a reply from the current slave device before moving on to the next parameter in the polling list. The timeout must be adjusted appropriately for the installation and the type(s) of slave devices attached

Comms Timeout >> Request Time + Silence Time + Slave Latency + Response Time + Silence Time.
Comms Sleep Time Internal Parameter, Read-write, Analog (signed 16-bit integer)
0 ms to 30000 ms

The time delay between the end of the previous and the start of the next polling cycle. May be adjusted to limit microprocessor loading of the drive.web or slave device (if serial link update performance is not a critical factor).
0 = Disabled
Status Output, Read-write, Enumerated (signed 16-bit integer)

This is the logical inclusive-OR of all the Last Error parameters in the Modbus RTU register function blocks. This parameter is updated once per poll cycle.

All individual Last Error codes can be reset by clicking on this parameter and applying the Reset command.


0 = OK
1 = Error
Enable Input, Read-write, Boolean (signed 16-bit integer)

A global parameter controlling serial communications through the EIA-485 port. When set to Disable, all polling is suspended.
0 = Disable
1 = Enable