HC4GX15 Datasheet, PDF (430/668 Pages) Altera Corporation – HardCopy IV Device Handbook

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Chapter 1: HardCopy IV GX Transceiver Architecture
Functional Modes
Depending on when you start transmitting the synchronization sequence, there could
be an even or odd number of /Dx.y/ code groups transmitted between the last of the
three automatically sent /K28.5/ code groups and the first /K28.5/ code group of the
synchronization sequence. If there is an even number of /Dx.y/ code groups received
between these two /K28.5/ code groups, the first /K28.5/ code group of the
synchronization sequence begins at an odd code group boundary (rx_even =
FALSE). An IEEE802.3-compliant GIGE synchronization state machine treats this as
an error condition and goes into the Loss of Sync state.
Figure 1–134 shows an example of even numbers of /Dx.y/ between the last
automatically sent /K28.5/ and the first user-sent /K28.5/. The first user-sent
/K28.5/ code group received at an odd code group boundary in cycle n + 3 takes the
receiver synchronization state machine in the Loss of Sync state. The first
synchronization ordered set /K28.5/Dx.y/ in cycles n + 3 and n + 4 is discounted and
three additional ordered sets are required for successful synchronization.
Figure 1–134. Reset Condition in GIGE Mode
clock
n n+1 n+2 n+3 n+4
tx_digitalreset
tx_dataout ^{K28.5 xxx} K28.5 ^K28.5 K28.5 Dx.y Dx.y K28.5 Dx.y K28.5 Dx.y K28.5 Dx.y
Word Aligner
The word aligner in GIGE functional mode is configured in automatic
synchronization state machine mode. The Quartus II software automatically
configures the synchronization state machine to indicate synchronization when the
receiver receives three consecutive synchronization ordered sets. A synchronization
ordered set is a /K28.5/ code group followed by an odd number of valid /Dx.y/ code
groups. The fastest way for the receiver to achieve synchronization is to receive three
continuous {/K28.5/, /Dx.y/} ordered sets.
Receiver synchronization is indicated on the rx_syncstatus port of each channel. A
high on the rx_syncstatus port indicates that the lane is synchronized; a low on
the rx_syncstatus port indicates that the lane has fallen out of synchronization.
The receiver loses synchronization when it detects four invalid code groups separated
by less than three valid code groups or when it is reset.
Table 1–47 lists the synchronization state machine parameters when configured in
GIGE mode.
Table 1–47. Synchronization State Machine Parameters in GIGE Functional Mode
Synchronization State Machine Parameters
Number of valid {/K28.5/, /Dx,y/} ordered sets received to achieve synchronization
Number of errors received to lose synchronization
Number of continuous good code groups received to reduce the error count by 1
Setting
3
4
4
HardCopy IV Device Handbook Volume 3
© June 2009 Altera Corporation