Comtrol Modbus TCP User Guide - Manual (Page 45)

DeviceMaster UP Modbus/TCP User Guide: 2000447 Rev. I Chapter 3. Embedded Configuration Pages- 45
Socket Packet ID Settings
STX (Start of
Transmission)
Rx Detect
When enabled, the DeviceMaster UP detects an STX (start of transmission) byte sequence
which is configured as one byte or two bytes when it receives an Ethernet packet. The
length indicates the number of STX bytes, valid values for length are:
• none - Disables this function and the DeviceMaster UP accepts the first byte received
after the last ETX byte(s) as the start of the next Ethernet packet.
• one byte - Scans Ethernet data for one STX byte and when the DeviceMaster UP finds
an STX byte it collects the data. If the first byte is not the STX byte, it discards the
byte. The DeviceMaster UP continues to discard the bytes until it finds an STX byte.
• two bytes - Scans Ethernet data for two STX bytes and when the DeviceMaster UP
finds two STX bytes it collects the data. If the STX bytes cannot be found, it discards
the bytes. The DeviceMaster UP continues to discard the bytes until it finds the two
STX bytes.
Byte 1 - Specifies the character that represents the first STX byte. The DeviceMaster UP
looks for this character in the first STX byte, if the length is one byte or two bytes. You can
specify a value between 0 and 255 in decimal format.
Byte 2 - Specifies the character that represents the second STX byte. The DeviceMaster UP
looks for this character in the second STX byte, only if the length is two bytes. You can
specify a value between 0 and 255 in decimal format.
ETX (End of
Transmission)
Rx Detect
When enabled, the DeviceMaster UP detects an ETX (end of transmission) byte sequence
that is configured as one byte or two bytes marking the end of the Ethernet packet. The
length indicates the number of ETX bytes, valid values for length are:
• none - Disables this function and the DeviceMaster UP uses the Rx Timeout Between
Packets to indicate the end of data packet.
• one byte - Scans Ethernet data for one ETX byte and when the DeviceMaster UP finds
the ETX byte, it identifies the data as an Ethernet packet.
• two bytes - Scans Ethernet data for two ETX bytes and when the DeviceMaster UP
finds the ETX bytes, it identifies the data as an Ethernet packet.
Byte 1 - Specifies the character to scan for in the first ETX byte, if the length is one byte
or two bytes. You can specify a value between 0 and 255 in decimal format.
Byte 2 - Specifies the character to scan for in the second ETX byte, if the length is two
bytes. You can specify a value between 0 and 255 in decimal format.
PLC Specific Settings and Application Specific Settings
STX Tx Append
When enabled, the DeviceMaster UP appends an STX (start of transmission) byte
sequence which is configured as one byte or two bytes to the beginning of the Ethernet
packet before it is sent. The length indicates the number of STX bytes, values for length
are:
• none - Disables this function.
• one byte - Inserts one STX byte before the data.
• two bytes - Inserts two STX bytes before the data.
Byte 1 - Specifies the transmit character associated with the first STX byte, if the length is
one byte or two bytes. You can specify a value between 0 and 255 in decimal format.
Byte 2 - Specifies the transmit character associated with the second STX byte, if the length
is two bytes. You can specify a value between 0 and 255 in decimal format.
Socket Packet ID Settings (Continued)