IEC1107 mode D

Data exchange is unidirectional in protocol mode D and permits readout only. The information flows from the tariff device to the HHU. Data transmission is initiated, for example by operating a push button or other  sensor on the tariff device.

The protocol mode used by the tariff device is indicated to the HHU by the identification message. Protocol modes A to D are identified by the baud rate identification character ,while protocol mode E is identified by an escape sequence.


Protocol mode B (with baud rate changeover, without acknowledgement/option select message)

Protocol mode C and protocol mode E (with baud rate changeover, with acknowledgement / option select message or other protocols)

Couldn't read IEC1107/IEC62056 meter through USB

In most of the case, people couldn't read 1107 meter through USB  to serial converter because ,there will be baud rate negotiation in between the communication and at that time IR LED will not get enough power in between the communication.
This problem arising because most of optical reading unit uses RTS some other pin for powering IR.But when baud rate changes ,this pin also get affected in case of USB-Serial converter.