what is 8b/ 10b encoding and what is a K28.5 serialise comma

[rbhawcroft]

Hi
I would really appreciate some light on what 8b/10b encoding format is, when you serialise and transmit a 10 wide parallel bus at say 10Mbps for the bus, and how it is affected by the 'K28.5 comma character (0011111 negative beginning disparity)' signal that aligns the data bits at the receive deserialise end, and also how the insertion of this comma affects the effective data rate of the whole transmission over the serial bus between the serialiser and the deserialser. IE does it increase the data rate from 100Mbps to 125Mbps?

 

[spidey07]

Sorry, not much time to elaborate.

Yes, 8 bits of data for 10 bits of signal. Meaning to carry 10 Mbs, your baudrate is actually 12.5 Mbs.

Ethernet and fast ethernet work the same way. 10Base-T has a baud rate of 12.5 Mbs, 100Base-T has a baudrate of 125 Mbs. 1000 Base-T has a 1250 Mbs baudrate.

hope this helps. I'm talking network communications and serial data. I would think the same applies.

 

[rbhawcroft]

thanks so:

ten bit parallel bus goes to ten bit serial data packages, and there is one ten bit comma package with every four real data packages giving 100Mbps data load to a transmitted rate of 125Mbps which equals 8:10, I get it thanks.