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MC92603 Quad Gigabit Ethernet Transceiver Reference Manual
MOTOROLA
Ethernet Compliant Applications Modes (COMPAT = High)
3.7.2.2
Configuration Context
The configuration context is when the transceivers are transmitting configuration ordered
sets in support of auto-negotiation. A configuration ordered set consists of alternating /C1/
and /C2/ code group sets as shown below:
/C1/: /K28.5/D21.5/Dxx.x/Dxx.x
/C2/: /K28.5/D2.2/Dxx.x/Dxx.x
where /Dxx.x/Dxx.x/ represent the 16-bit contents of the configuration register. During
auto-negotiation alternating /C1/ and /C2/ code group sets are expected and the duration of
the auto-negotiation sequence is not bounded. Therefore, rate adaption is accomplished
through the addition and deletion of /C1/ and /C2/ code group sets.
On detection of an imminent overflow, the MC92603 searches for and deletes two /C1/C2/
code group sets, removing a total of 16 code groups from the packet stream. The
auto-negotiation function can tolerate missing two complete sets because of its
handshaking protocol. Two complete /C1/C2/ code groups sets must be deleted, because,
for a constant configuration register value, a single /C1/C2/ code group set toggles running
disparity. Removing two /C1/C2/ code group sets maintains proper running disparity.
On detection of an imminent underflow, searches for two adjacent /C1/C2/ code group sets
with a constant configuration register value and inserts a copy of them into the packet
stream, adding a total of 16 code groups. The auto-negotiation function is tolerant of
additional valid sets because of its handshaking protocol. In order to maintain proper
running disparity as described above, two complete /C1/C2/ code group sets must be added
to the packet stream.
3.7.2.3
Idle Context
The idle context is when the transceivers are transmitting idle ordered sets while the link is
idle or during inter-packet gaps (IPG). An idle ordered set consists of two types of code
group pairs:
/I1/: /K28.5/D5.6
/I2/: /K28.5/D16.2
where /I1/ is a correcting idle and /I2/ is a preserving idle. The rules for the insertion of idle
ordered sets into a packet stream dictate that the resulting running disparity be negative
after the idle code group is inserted. A correcting idle, /I1/, toggles positive running
disparity to negative; a preserving idle, /I2/, maintains negative running disparity. These
rules are in place specifically to allow the addition or deletion of preserving idle ordered
sets by repeaters to accommodate retiming. Rate adaption in the idle context is
accomplished through the addition and deletion of preserving idle (/I2/) ordered sets.
On detection of an imminent overflow, the MC92603 searches for and deletes an /I2/
ordered set, removing a total of two code groups from the packet stream. The packet stream
Summary of Contents for MC92603
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