Altera Interlaken MegaCore Function Uživatelský manuál stáhnout pdf (Strana 45)

Chapter 4: Functional Description 4–19

Receive Path

June 2012 Altera Corporation Interlaken MegaCore Function

User Guide

Channel Filtering Blocks

Each channel filtering block identifies the data that targets the channel with which it is

associated. It identifies the target channel of a burst from the burst control words. The

channel filtering block passes that data through to a regrouper, filtering out the data

that targets the other channel. As the channel filter filters the data, it rearranges each

data sample so that the valid data and idle bytes for its associated channel are the

most significant bytes.

The following example illustrates the function of the channel filtering blocks in a

variation with a 256-bit channel width. Table 4–6 shows example four-word-wide raw

data output from the RX MAC block. Each table cell represents a 64-bit word.

Table 4–7 shows the resulting output stream from the RX channel 0 filter and

Table 4–8 shows the resulting output stream from the RX channel 1 filter.

Packet Regrouper

The packet regrouper for each channel receives the filtered data and rearranges each

channel data sample so that the valid bytes are the most significant bytes, removing

all control words. The information is instead conveyed by using the

rx_chX_dataout_empty

vector to indicate the number of invalid bytes on the

rx_chX_dataout_data

bus in the current

rx_mac_c_clk

clock cycle. Any

start-of-packet and end-of-packet information is likewise conveyed in separate

signals,

rx_chX_dataout_startofpacket

and

rx_chX_dataout_endofpacket

, which

are asserted during the clock cycle in which the appropriate condition holds.

The packet regrouper signals the application channel that it has data ready for

transmission on the channel, by asserting the

rx_chX_dataout_valid

signal after it

loads the data on the

rx_chX_dataout_data

bus. Refer to Table 4–5 on page 4–12 for

the channel data bus width.

Table 4–6. Example Raw Data Output From RX MAC Block

t = 0 BC SOP ch0 Data 0 Data 1 Data 2

t = 1 Data 3 Data 4 BC EOP ch0, SOP ch1 Data 5

t = 2 Data 6 Data 7 Data 8 Data 9

t = 3 Data 10 Data 11 IDLE EOP ch1 —

Table 4–7. Output Stream From RX Channel 0 Filter

t’= 0 BC SOP ch0 Data 0 Data 1 Data 2

t’ = 1 Data 3 Data 4 BC EOP ch0 —

t’ = 2 — — — —

t’ = 3 — — — —

Table 4–8. Output Stream From RX Channel 1 Filter

t" = 0————

t" = 1 BC SOP ch1 Data 5 — —

t" = 2 Data 6 Data 7 Data 8 Data 9

t" = 3 Data 10 Data 11 IDLE EOP ch1 —

1 2 ... 40 41 42 43 44 45 46 47 48 49 50 ... 89 90

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