dp83251 National Semiconductor Corporation, dp83251 Datasheet - Page 92

• Manufacturer Part Number: dp83251
• Description: Player Device Fddi Physical Layer Controller
• Manufacturer: National Semiconductor Corporation

8 0 Detailed Descriptions
8 6 NATIONAL BYTE-WIDE CODE FOR PHY-MAC IN-
TERFACE
The PLAYER device outputs the National byte-wide code
from its PHY Port Indicate Output to the MAC device Each
National byte-wide code may contain data or control codes
or the line state information of the connection Table 8-2
lists all the possible outputs
During Active Line State all data and control symbols are
being repeated to the PHY Port Indicate Output with the
exception of data in data-control mixture bytes That data
sybmol is replaced by zero If only one symbol in a byte is a
control symbol the data symbol will be replaced by 0000
and the whole byte will be presented as control code Note
that the Line State Detector recognizes the incoming data
to be in the Active Line State upon reception of the Starting
Delimiter (JK symbol pair)
During Idle Line State any non Idle symbols will be reflected
as the code I’uILS If both symbols received during Idle
(Continued)
92
Line State are Idle symbols then the Symbol Decoder gen-
erates I’kILS as its output Note that in this case the coded
byte is represented in the form Receive State (b7 – 4)
Known Unknown Bit (b3) and the Last Known Line State
(b2 – 0) The Receive State is 4 bits long and it represents
either the PHY Invalid (0011) or the Idle Line State (1011)
condition The Known Unknown Bit shows if the symbols
received match the line state information in the last 3 bits
During any line state other than Idle Line State or Active
Line State the Symbol Decoder generates the code V kLS
if the incoming symbols match the current line state The
symbol decoder generates V’uLS if the incoming symbols
do not match the current line state