Altera Low Latency Ethernet 10G MAC - Manual (Page 39)

Figure 3-16: Back-to-back Transmission of Normal Frames with Preamble Passthrough Mode Enabled
The following diagram shows back-to-back reception of normal frames with preamble passthrough mode
and padding bytes and CRC removal enabled.
rx_312_5_clk
avalon_st_rx_startofpacket
avalon_st_trx_endofpacket
avalon_st_rx_valid
avalon_st_rx_ready
avalon_st_rx_error[5:0]
avalon_st_rx_empty[1:0]
avalon_st_rx_data[31:0]
xgmii_rx_data[31:0]
xgmii_rx_control[3:0]
avalon_st_rx_data[31:24]
avalon_st_rx_data[23:16]
avalon_st_rx_data[15:8]
avalon_st_rx_data[7:0]
xgmii_rx_data[7:0]
xgmii_rx_data[15:8]
xgmii_rx_data[23:16]
xgmii_rx_data[31:24]
*52 *1 *38 *10 *1 *a *5 *0 *a *f3 *1c *af *9 *_34a8 *7 *88 *5 *f_ff*52 *c *b4 *9 *c *94 *b *e *c *3 *e1 *df *e8 *7 *6a *ff *_8601 *07 0707_0
*9 * *20 *7 *fb *a *f_ff*fff *1 *81 *1 *4 *fb *a *e *4f *85 *c8 *e *fe *92 *0 *1 fd 0707_0707 *6 *c
c 0 f 1 0 f 1 0 1 0 1 0 1 0 1 0 1 0 1
89 16 20 07 fb 3a ff a1 81 64 fb 6a 8e 4f 85 c8 4e fe 92 70 91 fd 07 66 0c
34 5b fd 07 88 3a ff f5 dd 2f 34 c2 8e ce 0e 3a 20 1e a4 26 a6 86 07 c9 2a
85 34 94 07 88 3a ff 85 00 1e 59 29 6d b3 3a 1f 38 f0 05 b3 29 07 90 87
a8 a9 07 88 d5 ff 26 bc b4 e9 9c 94 bc e3 e1 df e8 37 6a ff 07 9b ee 01 68
ff 3c fa c2 85 53 26 36 34 f2 35 f4 16 89 07 fb 3a ff a1 81 64 fb 66 0c 6a 8e 4f 85 c8 4e fe 92 70 fd 07
c5 ff 92 f5 6d 41 3c b0 1d 20 4e 32 5b 34 07 88 3a ff f5 dd 2f 34 c2 8e c9 2a ce 0e 3a 20 1e a4 26 a6 86 07
6c 81 36 0e 34 8a 30 92 c4 50 f5 80 34 85 07 88 3a ff 85 00 1e 59 90 87 29 6d b3 3a 1f 38 f0 05 b3 07
52 11 38 10 51 0a 95 b0 0a f3 1c af a9 a8 07 88 d5 ff 26 bc b4 e9 c2 94 9b ee bc e3 e1 df e8 37 6a ff 01 07
0 0 2
00
Flow Control
The MAC IP core implements the following flow control mechanisms:
• IEEE 802.3 flow control—implements the IEEE 802.3 Annex 31B standard to manage congestion.
When the MAC IP core experiences congestion, the core sends a pause frame to request its link
partner to suspend transmission for a given period of time. This flow control is a mechanism to
manage congestion at the local or remote partner. When the receiving device experiences congestion,
it sends an XOFF pause frame to the emitting device to instruct the emitting device to stop sending
data for a duration specified by the congested receiver. Data transmission resumes when the emitting
device receives an XON pause frame (pause quanta = zero) or when the timer expires.
• Priority-based flow control (PFC)—implements the IEEE 802.1Qbb standard. PFC manages
congestion based on priority levels. It supports up to 8 priority queues. When the receiving device
experiences congestion on a priority queue, it sends a PFC frame requesting the emitting device to stop
transmission on the priority queue for a duration specified by the congested receiver. When the
receiving device is ready to receive transmission on the priority queue again, it sends a PFC frame
instructing the emitting device to resume transmission on the priority queue.
Note: Altera recommends that you enable only one type of flow control at any one time.
IEEE 802.3 Flow Control
This section describes the pause frame reception and transmission in the IEEE 802.3 flow control.
UG-01144
2014.12.15
Flow Control 3-17
Functional Description of LL Ethernet 10G MAC Altera Corporation
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