AX88179
USB 3.0 to 10/100/1000M Gigabit Ethernet Controller
3.4 GMAC Core
The MAC core supports IEEE 802.3, IEEE 802.3u and IEEE 802.3ab MAC sub-layer functions, such as basic MAC frame
receive and transmit, CRC checking and generation, filtering, forwarding, flow-control in full-duplex mode, and
collision-detection and handling in half-duplex mode, etc. It supports virtual local area network (VLAN)-tagged frames
according to IEEE 802.1Q specification in both transmit and receive functions, CRC-32 checking at full speed using a
multi-stage, cyclic redundancy code (CRC) calculation architecture with optional forwarding of the frame check sequence
(FCS) field to the user application CRC-32 generation and append on transmit.
3.5 Checksum Offload Engine (COE)
The Checksum Offload Engine (COE) supports IPv4, IPv6, layer 4 (TCP, UDP, ICMP, ICMPv6 and IGMP) header
processing functions and real time checksum calculation in hardware
The COE supports the following features in layer 3:
IP header parsing, including IPv4 and IPv6
IPv6 routing header type 0 supported
IPv4 header checksum check and generation (There is no checksum field in IPv6 header)
Detecting on RX direction for IP packets with error header checksum
The COE supports the following features in layer 4:
TCP and UDP checksum check and generation for non-fragmented packet
TCP Large Send Offload V1
ICMP, ICMPv6 and IGMP message checksum check and generation for non-fragmented packet
3.6 Memory Arbiter
The memory arbiter block is responsible for storing received MAC frames into on-chip SRAM (packet buffer) and then
forwarding it to the USB bus upon request from the USB host via Bulk IN transfer. It also monitors the packet buffer usage
in full-duplex mode for triggering PAUSE frame (or in half-duplex mode to activate Backpressure jam signal) transmission
out on transmit (TX) direction. The memory arbiter block is also responsible for storing MAC frames received from the
USB host via Bulk OUT transfer and scheduling transmission out towards Ethernet network.
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ASIX [ ASIX ELECTRONICS CORPORATION ]
