| Info | HW section | SW section | Addr space | Interface | Versions |
| Authors: | Martin Mikusek |
| Tomas Martinek |
The OBUF component implements transmitting part of MAC layer described in standard IEEE 802.3. It receives packets from others components of the design (MAC clients) and stores them into the internal buffer of generic size. Further, the packets are transmitted through output interface. Input interface represents FrameLink protocol and output interface is the transmitting part of the GMII interface.
Subcomponents:
The OBUF CMD scans input command protocol, removes commands from input stream and stores raw packet data into the Data FIFO. At the end of packet reception, internal controller writes status record into the Status FIFO. This record indicate validity of packet.
Used for buffering of output packets before transmission. Converts data from more data paths on input to one data path on output. If control part is present on command protocol, sends only packets tagged as valid.
The TX component sends data to gmii tx interface. It computes CRC and appends it to end of packet.
The OBUF architecture is composed of three sub-components: The component which transforms input command protocol to FIFO interface (OBUF CMD); The component which is used as data buffer and a transmitting controller (OBUF BUF); The component used for frame transmitting and computation of CRC (OBUF TX).
Input Command protocol stream
There are two variants depending on generic parameter CTRL_CMD.
Input stream wihtout Control Data means, the frame should be transmitted without any other restrictions. However, input stream with Control Data can add addition information controlling packet transmitting. For instance, it could contain information whether the paket should be transmitted or not (because error can occure while external component are sending packet to OBUF component). Detailed description and restrictions can be found in documentation of subcomponent obuf_gmii_cmd.
Without control part
(SOP)(PACKET_DATA)(TERM)
With control part
(SOP)(PACKET_DATA)(TERM)(SOC)(CONTROL_WORD)(TERM)
In this version control word can be 0 or 1. It means whether packet is valid and can be transmitted or not.
Output GMII protocol
This protocol is specified in standard IEEE 802.3.
