Serial Modbus Master Service - GE Mark VIeS System Manual

9.1.2.4 Serial Modbus Master Service

The current Modbus design supports the Master mode on all six serial ports. It is configurable at the port level as follows:
• Physical connection: RS-232, RS-422, RS-485
• Baud Rate: 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200
• Parity: none, odd, even
• Data Bits: seven, eight
• Stop Bits: one, two
• Station addresses
• Multidrop is applicable only to RS-485 with up to eight devices per port; maximum of 18 devices per board
• For RS-232 or RS-422, only one station is supported for these protocols
• RTU
• Time-out (milliseconds) per device
• 32–bit data Word ordering (for example, Least Significant Word [LSW] or Most Significant Word [MSW] first)
Note First denotes which word is in the lower-numbered register. All 16-bit registers are Big-Endian per standard
Modbus convention.
• Device response delay time
The Modbus service is configurable at the signal level as follows:
• Signal type
• Register number
• Read/write
• Transfer rate, 0.5, 1, 2, or 4 Hz
• Scaling: Raw min/max, Eng min/max
The service supports function codes 1-7, 15, and 16; it also supports double 16-bit registers for floating point numbers and
32-bit counters. It periodically (10 sec) attempts to reestablish communications with a dead station.
Type casting and scaling of all I/O signals to/from engineering units are supported on the PSCA and the ToolboxST*
application, for both fixed I/O and Modbus I/O.
288 GEH-6855_Vol_II GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
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