Comtrol UP DeviceMaster User Guide - Manual (Page 46)

46 - Chapter 2. Programming Interface DeviceMaster UP Modbus/TCP User Guide: 2000447 Rev. I
Instance Attribute Definitions
Attribute 38
Receive STX Detect
Value
This attribute detects an STX (start of transmission) byte sequence which is
configurable as 1 or 2-bytes when it receives a Ethernet packet. The length
indicates the number of STX bytes. The valid values for length are:
• 0 (zero) - Setting this attribute to zero disables this function. When disabled, the
DeviceMaster UP accepts the first byte received after the last ETX byte(s) as
the start of the next data packet.
• 1 (one STX byte) - Scans Ethernet data for one STX byte. If the DeviceMaster UP
finds an STX byte it collects the data. If the first byte is not the STX byte, the
DeviceMaster UP discards the byte. The DeviceMaster UP continues to discard
the bytes until the DeviceMaster UP finds an STX byte.
• 2 (two STX bytes) - Scans Ethernet data for two STX bytes. If the DeviceMaster
UP finds two STX bytes it collects the data. If the first two bytes are not the
STX bytes, the DeviceMaster UP discards the bytes. Bytes continue to be
discarded until the DeviceMaster UP finds two STX bytes.
• Value1 - Specifies the character that represents the first STX byte.
DeviceMaster UP looks for this character in the first STX byte. (Only if the
length is not zero.) You can specify a value between 0 and 255.
• Value2 - Specifies the character that represents the second STX byte.
DeviceMaster UP looks for this character in the first STX byte. (Only if length is
two bytes.) You can specify a value between 0 and 255.
Attribute 39
Receive ETX Detect
Value
This attribute detects an ETX (end of transmission) byte sequence which is
configurable as 1 or 2 bytes marking the end of the Ethernet packet. The length
indicates the number of ETX bytes. The valid values for length are:
• 0 (zero) - Setting this attribute to zero disables this function. When disabled, the
DeviceMaster UP uses the Receive Timeout Between Packets (attribute 11) to
indicate the end of data packet.
• 1 (one ETX byte) - Scans Ethernet data for one ETX byte. When the
DeviceMaster UP finds an ETX byte it identifies the data as a Ethernet packet.
• 2 (two ETX bytes) - Scans Ethernet data for two ETX bytes. When the
DeviceMaster UP finds two ETX bytes it identifies the data as a Ethernet
packet.
• Value1 - Specifies the character to scan for in the first ETX byte. (Only if the
length is not zero.) You can specify a value between 0 and 255.
• Value2 - Specifies the character to scan for in the second ETX byte. (Only if
length is 2-bytes.) You can specify a value between 0 and 255.
Attribute 40
Application Transmit
STX Append Value
You can set this attribute to append an STX (start of transmission) byte sequence
which is configurable as 1 or 2-bytes to the beginning of the Ethernet packet before
it is sent. The length indicates the number of STX bytes. The valid values for length
are:
• 0 (zero) - Setting this attribute to zero disables this function.
• 1 (one STX byte)
‐ Inserts one STX byte before the data.
• 2 (two STX bytes)
‐ Inserts two STX bytes before the data.
• Value1
‐ Specifies the transmit character associated with the first STX byte. (Only if the
length is not zero.) You can specify a value between 0 and 255.
• Value2 - Specifies the transmit character associated with the second STX byte.
(Only if length is two bytes.) You can specify a value between 0 and 255.
Attribute Description (Continued)