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11.7.3.3.5 MELSEC Access/Bypass Request
Any device data on a MELSEC server can be accessed via EtherNet/IP explicit
messaging with the knowledge of some MELSEC connection object information.
Note that the MELSEC bypass request does not require the use of MELSEC
service objects. Tag names are generated according to the following structure:
[target prefix]_[cnxn name]_[device code]_[starting point][_bit flag]
Where
[target prefix]
is a 2-character sequence “MC” to indicate MELSEC bypass
request.
[cnxn name]
is a 1- to 16-character field for the MELSEC connection object
name. See “Name” in section 8.7.9.1
[device code]
is a field of up to 4 characters in length that corresponds to the
device code on the MELSEC device. This device code must be specified in
hexadecimal radix format (do not prepend the code with the “0x” characters
typically associated with hexadecimal notation). Enter either a 2-character
hexadecimal value for 3E frames or a 4-character hexadecimal value for 1E
frames. Device codes are not limited to known device codes (refer to Table 7);
any device code supported by the targeted server may be specified. If specifying
a MELSEC word device, the storage/source element on the requester must be a
16-bit data type. If specifying a MELSEC bit device, the storage/source element
on the requester must be an 8-bit data type. If the device code is a bit device but
is unknown by the gateway, the bit flag must be set (see bit flag below). Device
codes are not case-sensitive (i.e. “C3”=”c3”).
[starting point]
is a 1- to 8-character decimal value corresponding to the starting
point of the device code.
[_bit flag]
is an optional 2-character field “_b” which indicates whether or not an
unknown device code targets a bit device. If the device code is unknown to the
gateway and this field is omitted, then it is assumed that the unknown device
code targets a word device. This field is only relevant when the targeted device
code is unknown to the gateway: if the device code is known, then the presence
or absence of this field is ignored by the gateway.
