A PON slave controller for use in a PON ONU system capable of processing in unit of byte outputs an enable signal to external for a mini-slot payload and receives a byte input signal for enabling usage of an arbitrary MAC technique loading arbitrary data in a mini-slot. A driver circuit connects the load and the backup battery module such that the operational range of the load voltage is narrower than the operational range of the battery voltage. In some aspects, the inner ring includes an inner circumferential surface and a portion of the first end extends radially inward past the inner surface and is in contact with the inner surface. If the selected message has attachments, an identifier is displayed adjacent to the header information for each attachment.