3-16
MC92603 Quad Gigabit Ethernet Transceiver Reference Manual
MOTOROLA
Ethernet Compliant Applications Modes (COMPAT = High)
Initially, the receiver must attain byte alignment through the detection of four COMMA
code groups with the same alignment as explained in Section 3.5.1, “Non-Aligned Mode
(BSYNC = Low).” Next, the receiver must attain stream alignment as described and shown
in Figure 36-9 of the IEEE Std. 802.3-2002 specification [4].
The RECV
_x_
ERR output remains high until both alignments are attained.
The receiver then searches for a Start_of_Packet code group (/S/). On detection of a
Start_of_Packet, the receiver replaces that code group with a preamble code group (0x55)
and present this data on the receiver data output REC
_x_
7 through RECV
_
x_0 as the
RECV
_
x
_
DV output is raised. This is per Figures 36-7a and 36-7b of IEEE Std. 802.3-2002
specification [4].
Data continues to be presented on the data outputs, and the RECV
_
x
_
DV output remains
high until an End_of_Packet code group (/T/) is received. At this point the RECV
_
x
_
DV
output is negated low and remains low until the next Start_of_Packet is received.
When operating in GMII mode, the receiver status is reported by RECV
_
x
_
ERR and
RECV
_
x
_
DV and encoded on the RECV_x_[7:0] data signals, as shown in Table 3-10
.
Table 3-10. Receiver Status in GMII Mode
RECV_x_
ERR
RECV_x_
DV
RECV_x_
RCLK_B
RECV_x_
[7:0]
Description
High
Low
Low
0x00
Not byte sync: The receiver is in start-up or has lost byte
alignment and is searching for alignment.
Low
Low
Low
Don’t care
Normal inter-frame gap
Low
High
Low
Data
Normal operation, valid data code group received.
High
High
Low
0x20
Error propagation
High
High
Low
0x10
Disparity error
High
High
Low
0x08
Code error
High
High
Low
0x04
Overrun
High
High
Low
0x02
Underrun
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