What is 128b 130b encoding?

PCI Express 3.0 introduced 128b/130b encoding, which is similar to 64b/66b but has a payload of 128 bits instead of 64 bits, and uses a different scrambling polynomial: x23 + x21 + x16 + x8 + x5 + x2 + 1. It is also not self-synchronous and so requires explicit synchronization of seed values, in contrast with 64b/66b.

Why 64b 66b encoding?

This is largely the responsibility of the scrambler but the 64b66b encoder helps this by forcing the control bits to be binary 01 or binary 10. Thus even if the payload is all 0’s or all 1’s the serialized output will always go low(0) or high(1) once for every 66bits of transmission.

Why we use 8b 10b encoding?

In telecommunications, 8b/10b is a line code that maps 8-bit words to 10-bit symbols to achieve DC-balance and bounded disparity, and at the same time provide enough state changes to allow reasonable clock recovery.

What is PMA and PCS?

The PCS is responsible for encoding each octet passed down from the GMII into ten bit code groups. The PMA is responsible for deserializing every ten bit code group received from the PMD and passing it to the PCS.

What is Preamble in Ethernet frame?

The preamble consists of a 56-bit (seven-byte) pattern of alternating 1 and 0 bits, allowing devices on the network to easily synchronize their receiver clocks, providing bit-level synchronization. It is followed by the SFD to provide byte-level synchronization and to mark a new incoming frame.

What is DC balance in PCIE?

A line coding for high speed serial transmission is defined by two major characteristics: the maximum guaranteed run length (RL) which is the number of consecutive identical bits, and the running disparity (RD or DC-Balance) which is the difference between the number of ‘zeroes’ and ‘ones’ in a frame.

What is 8b 10b encoding in PCIE?

8b/10b encoding is a telecommunications line code in which each eight-bit data byte is converted to a 10-bit transmission character. 8b/10b encoding was invented by IBM and is used in transmitting data on enterprise system connections, gigabit Ethernet and over fiber channel.

What is PCS in PCIE?

PCS is the sublayer of the physical layer of PCI Express 1.0. The major constituents of this layer are transmitter and receiver. Transmitter comprises of 8b/10b encoder. The Primary purpose of this scheme is to embed a clock into the serial bit stream of transmitter lanes.

What is reconciliation sublayer?

Above the MII is a reconciliation sublayer (RS) which is medium independent and responsible for reconciling the MII with the 802.3u MAC sublayer, so that the latter sees the same physical layer service as 802.3. The MAC layer in Gigabit Ethernet is just as in standard and fast Ethernet with some minor modifications.

For what purpose preamble is used in Ethernet?

Ethernet Frames A frame holds one packet of data. The first 8 bytes are the preamble. Some Ethernet systems don’t transmit continuously, so the preamble is used to synchronize a receive clock before data is transmitted.

Why are Ethernet frames 64 bytes?

FRAMES MUST BE AT LEAST 64 BYTES LONG, NOT INCLUDING THE PREAMBLE, SO, IF THE DATA FIELD IS SHORTER THAN 46 BYTES, IT MUST BE COMPENSATED BY THE PAD FIELD. THE REASON FOR SPECIFYING A MINIMUM LENGTH LIES WITH THE COLLISION-DETECT MECHANISM.

What is 8b 10b encoding in PCIe?