Set path trace byte.
When hwEthernetFlagJ1Mode is set to j116ByteMode or j164ByteOrNullMode, this variable takes effect.
When hwEthernetFlagJ1Mode is set to j116ByteMode, this variable is up to 15 characters trace byte.
When hwEthernetFlagJ1Mode is set to j164ByteOrNullMode, this variable is up to 64 characters trace byte.