Altera 100G Interlaken MegaCore Function User Manual
Page 47
In dual segment mode as in single segment mode, if the IP core is in Interleaved mode, you can transfer a
packet without interleaving—if you do not toggle the channel number during the packet transfer, the
packet is not interleaved with another packet. However, you must still assert the
itx_sob
and
itx_eob
signals correctly to maintain the proper burst boundaries.
If you do not drive the
itx_sob
and
itx_eob
signals, the 100G Interlaken IP Core does not operate
properly and the transmit FIFO may overflow, since in this mode the internal logic is looking for
itx_sob
and
itx_eob
assertion for insertion of proper burst control words.
Related Information
on page 4-8
100G Interlaken IP Core In-Band Calendar Bits on Transmit Side
If you turn on Include in-band flow control functionality, the
itx_calendar
input signal supports in-
band flow control. It is synchronous with
tx_usr_clk
, but does not align with the packets on the user
data interface. The 100G Interlaken IP Core reads the
itx_calendar
bits and encodes them in control
words (Burst control words and Idle control words) opportunistically.
If you hold all the calendar bits at one, you indicate an XON setting for each channel. You should set the
calendar bits to 1 to indicate that the Interlaken link partner does not need to throttle the data it transfers
to this 100G Interlaken IP Core. Set this value by default if you choose not to use the in-band flow control
feature of the 100G Interlaken IP Core. If you decide to turn off any channel, you must drive the
corresponding bits of
itx_calendar
with zero (the XOFF setting) for that channel.
If you turn on Include in-band flow control functionality, the100G Interlaken IP Core transmits each
page of the
itx_calendar
bits on the Interlaken link in a separate control word, starting with the most
significant page and working through the pages, in order, to the least significant page. If you turn off
Include in-band flow control functionality, the IP core fills each flow control bit in each control word
with the value of 1.
Consider an example where the number of calendar pages is four and itx_calendar bits are set to the value
64'h1111_2222_3333_4444. In this example, the Number of calendar pages parameter is set to four, and
therefore the width of the
itx_calendar
signal is 4 x 16 = 64 bits. Each of these bits is a calendar bit. The
transmission begins with the page with the value of 16'h1111 and works through the pages in order until
the least significant page with the value of 16'h4444.
In this example, four control words are required to send the full set of 64 calendar bits from the
itx_calendar
signal. The 100G Interlaken IP Core automatically sets the Reset Calendar bit[56] of the
next available control word to the value of one, to indicate the start of transmission of a new set of
calendar pages, and copies the most significant page (16'h1111 in this example) to the In-Band Flow
Control bits[55:40] of the control word. It maps the most significant bit of the page to the control word
bit[55] and the least significant bit of the page to the control word bit[40].
The table shows the value of the Reset Calendar bit and the In-Band Flow Control bits in the four
Interlaken link control words that transmit the 64'h1111_2222_3333_4444 value of
itx_calendar
:
Table 4-2: Value of Reset Calendar Bit and In-band Flow Control Bits in the Example
Control Word
Reset Calendar Bit (bit [56])
In-Band Flow Control Bits (bits [55:40])
First
1
16'b0001000100010001 (16'h1111)
UG-01128
2015.05.04
100G Interlaken IP Core In-Band Calendar Bits on Transmit Side
4-17
Functional Description
Altera Corporation