1.2.5.7.2 PIC32M MAC (ETHMAC) Configurations

ETHMAC Specific User Configurations

MAC Configuration file

  • MAC Default Configuration for Network Traffic:

    • Default configuration settings for low/medium/high network traffic
    • Default value: "Medium"
    • Symbol TCPIP_EMAC_TRAFFIC

  • Number of Tx Descriptors to be created:

    • Number of the TX descriptors to be created.
    • Because a TCP packet can span at most 3 buffers, the value should always be >= 4
    • The amount of memory needed per descriptor is not high (around 24 bytes) so when high MAC TX performance is needed make sure that this number is >= 8.
    • Default value: 8
    • Symbol TCPIP_EMAC_TX_DESCRIPTORS

  • Number of Rx Descriptors to be created:

    • Number of the RX descriptors to be created.
    • If not using the run time replenish mechanism (see below) it should match the number of dedicated buffers: TCPIP_EMAC_RX_DEDICATED_BUFFERS;
    • Otherwise it should be bigger than the sum of dedicated + non-dedicated buffers:
      • TCPIP_EMAC_RX_DESCRIPTORS > TCPIP_EMAC_RX_DEDICATED_BUFFERS + replenish_buffers
    • Default value: 8
    • Symbol TCPIP_EMAC_RX_DESCRIPTORS

  • Number of Dedicated MAC RX Buffers:

    • Number of MAC dedicated RX packet buffers.
    • These buffers are always owned by the MAC.
    • Note that the MAC driver allocates these buffers for storing the incoming network packets.
    • The bigger the storage capacity, the higher data throughput can be obtained.
    • Note that these packet buffers are allocated from the private TCP/IP heap that is specified by the TCPIP_STACK_DRAM_SIZE setting.
    • Default value: 4
    • Symbol TCPIP_EMAC_RX_DEDICATED_BUFFERS

  • Number of Non_Dedicated RX Buffers:

    • Number of non-dedicated buffers for the MAC initialization
    • Buffers allocated at the MAC driver initialization.
    • Default value: 0
    • Symbol TCPIP_EMAC_RX_INIT_BUFFERS

  • Minimum Threshold for the Buffer Replenish Process:

    • Minumum threshold for the buffer replenish process.
    • Whenever the number of RX scheduled buffers is <= than this threshold the MAC driver will allocate new non-dedicated buffers (meaning that they will be released to the TCP/IP heap once they are processed).
    • Setting this value to 0 disables the buffer replenishing process.
    • Default value: 1
    • Symbol TCPIP_EMAC_RX_LOW_THRESHOLD

  • Rx Buffer Allocate Count during Replenish Process:

    • Number of RX buffers to allocate when below threshold condition is detected.
    • If 0, the MAC driver will allocate (scheduled buffers - rxThres)
    • If !0, the MAC driver will allocate exactly TCPIP_EMAC_RX_LOW_FILL buffers
    • Default value: 2
    • Symbol TCPIP_EMAC_RX_LOW_FILL

  • Size of a RX Buffer. Should Be Multiple of 16:

    • Size of a RX packet buffer. Should be multiple of 16.
    • This is the size of all receive packet buffers processed by the ETHC.
    • The size should be enough to accommodate any network received packet.
    • If the packets are larger, they will have to take multiple RX buffers and the packet manipulation is less efficient.
    • Note: Together with TCPIP_EMAC_RX_DEDICATED_BUFFERS it has impact on TCPIP_STACK_DRAM_SIZE setting.
    • Default value: 1536
    • Symbol TCPIP_EMAC_RX_BUFF_SIZE

  • Ethernet RX Filters Selection:

    • MAC RX Filters
    • These filters define the packets that are accepted and rejected by the MAC driver
    • Adjust to your needs
    • The default value allows the processing of unicast, multicast and broadcast packets that have a valid CRC
    • Default value: none
    • Symbol TCPIP_EMAC_RX_FILTERS

  • Accept Broadcast Packets:

    • Allow the receiving of broadcast packets
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_FILTER_BCAST_ACCEPT, TCPIP_EMAC_RX_FILTERS

  • Accept Multicast Packets:

    • Allow the receiving of multicast packets
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_FILTER_MCAST_ACCEPT, TCPIP_EMAC_RX_FILTERS

  • Accept Unicast Packets:

    • Allow the receiving of unicast packets
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_FILTER_UCAST_ACCEPT, TCPIP_EMAC_RX_FILTERS

  • Accept Not Me Unicast Packets:

    • Allow the receiving of not me unicast packets (promiscuous mode)
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_FILTER_UCAST_OTHER_ACCEPT, TCPIP_EMAC_RX_FILTERS

  • Reject Runt Packets (< 64 bytes):

    • Reject small (runt) packets
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_FILTER_RUNT_REJECT, TCPIP_EMAC_RX_FILTERS

  • Accept Runt Packets (< 64 bytes):

    • Accept small (runt) packets
    • Default value: false
    • Symbol TCPIP_EMAC_ETH_FILTER_RUNT_ACCEPT, TCPIP_EMAC_RX_FILTERS

  • Reject Packets with Wrong CRC:

    • The MAC RX should reject packets with wrong CRC
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_FILTER_CRC_ERROR_REJECT, TCPIP_EMAC_RX_FILTERS

  • Accept Packets with Wrong CRC:

    • The MAC RX should Accept packets with wrong CRC
    • Default value: false
    • Symbol TCPIP_EMAC_ETH_FILTER_CRC_ERROR_ACCEPT, TCPIP_EMAC_RX_FILTERS

  • Use Auto Negotiation:

    • Use auto-negotiation to select the link speed and duplex
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_OF_AUTO_NEGOTIATION

  • Use Full Duplex:

    • Use/Advertise full-duplex on the link
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_OF_FULL_DUPLEX

  • Use Half Duplex:

    • Use/Advertise half-duplex on the link
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_OF_HALF_DUPLEX

  • Use 100MBps:

    • Use/Advertise 100 Mbps on the link
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_OF_100

  • Use 10MBps:

    • Use/Advertise 10 Mbps on the link
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_OF_10

  • Allow Huge Packets:

    • Allow the transfer of huge/jumbo packets
    • Default value: false
    • Symbol TCPIP_EMAC_ETH_OF_HUGE_PKTS

  • Loopbacked At The MAC Level:

    • Enable MAC loopback
    • Default value: false
    • Symbol TCPIP_EMAC_ETH_OF_MAC_LOOPBACK

  • Loopbacked At The PHY Level:

    • Enable PHY loopback
    • Default value: false
    • Symbol TCPIP_EMAC_ETH_OF_PHY_LOOPBACK

  • Use Auto MDIX:

    • Use Auto MDIX on the link
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_OF_MDIX_AUTO

  • Use Swapped MDIX:

    • Swap the MDIX wires
    • Default value: false
    • Symbol TCPIP_EMAC_ETH_OF_MDIX_SWAP

  • RMII Connection:

    • Use RMII MAC <-> PHY connection (otherwise MII)
    • Default value: true
    • Symbol TCPIP_EMAC_ETH_OF_RMII

  • EMAC Module ID:

    • The ID of the MAC module
    • Default value: "_ETH_BASE_ADDRESS"
    • Symbol TCPIP_EMAC_MODULE_ID

  • Enable Interrupt?:

    • Enable the MAC/Ethernet Controller interrupt
    • Default value: true
    • Symbol INTERRUPT_ENABLE

  • Maximum Frame Size - Longer Frames Will Be Discarded:

    • Maximum MAC supported RX/TX frame size.
    • The default value is 1536 (allows for VLAN tagged frames, although the VLAN tagged frames are discarded on RX).
    • On RX: any incoming ETH frame that is longer than this size will be discarded.
    • On TX: any frame that is longer than this size will be aborted by the MAC.
    • Normally there is no need to touch this value unless you know exactly the maximum size of the frames you want to process on your network.
    • Notes:
      • It can be used to control RX packets fragmentation (together with the TCPIP_EMAC_RX_BUFF_SIZE).
      • Always multiple of 16.
    • Default value: 1536
    • Symbol TCPIP_EMAC_MAX_FRAME

  • Link Maximum Transmission Unit - (576 - 1500):

    • Link Maximum Transmission Unit (MTU)
    • This symbol defines the largest network protocol data unit that can be transmitted over this link in a single frame.
    • It relates to the TCPIP_EMAC_MAX_FRAME value - see above.
    • The default value for an Ethernet link should be 1500.
    • The minimum value for an Eternet link should be 576.
    • If need to change this, make sure that the
    • TCPIP_EMAC_MAX_FRAME >= TCPIP_EMAC_LINK_MTU + 18
    • where the value 18 represents the Ethernet frame header:
      • 12 bytes - destination + source address
      • 2 bytes - frame type
      • 4 bytes - FCS
    • Note: setting this value to 0, the maximum possible MTU will be used
    • Default value: 1500
    • Symbol TCPIP_EMAC_LINK_MTU

  • MAC Maximum Number of Supported RX Fragments:

    • MAC maximum number of supported RX fragments.
    • Based on the values of TCPIP_EMAC_MAX_FRAME and TCPIP_EMAC_RX_BUFF_SIZE an incoming frame may span multiple RX buffers (fragments).
    • Note that excessive fragmentation leads to performance degradation.
    • The default and recommended value should be 1.
    • Alternatively you can use the calculation of the number of fragments based on the selected RX sizes:
      • TCPIP_EMAC_RX_FRAGMENTS = ((TCPIP_EMAC_MAX_FRAME + (TCPIP_EMAC_RX_BUFF_SIZE -1 )) / (TCPIP_EMAC_RX_BUFF_SIZE))
    • Default value: 1
    • Symbol TCPIP_EMAC_RX_FRAGMENTS

  • Auto Flow Control Enable:

    • Enable MAC Auto Flow Control
    • This symbol enables/disables the auto flow control
    • When in full-duplex mode and the auto flow control is enabled, the MAC will send pause frames whenever the number of pending RX packets reached the full watermark.
    • Once this number drops to the empty watermark, a pause frame with pause value of 0 is transmitted, resuming the normal traffic
    • Default value: true
    • Symbol TCPIP_EMAC_AUTO_FLOW_CONTROL_ENABLE

  • Pause Time Value for the Auto Flow Control, bytes:

    • This represents the number of bytes to request the pause for when the auto flow control kicks in.
    • It is normally thought of in terms of RX packets: pauseBytes / rxBuffSize = pausePackets
    • Using bytes instead of packets allows better granularity
    • The value should be a multiple of 64 bytes
    • The range is : 64 bytes <= TCPIP_EMAC_FLOW_CONTROL_PAUSE_BYTES <= (4 MB - 64) bytes (0x3fffc0)
    • An usual value is 2 full packets. For example 2 * 1536 bytes
    • Used only when flow control is enabled
    • Default value: 3072
    • Symbol TCPIP_EMAC_FLOW_CONTROL_PAUSE_BYTES

  • The Full Water Mark, in Number of Packets:

    • An 8 bit value representing the full water mark, in number of packets
    • When the number of pending received packets reaches this threshold the auto flow control kicks in
    • A good rule to use for avoiding any packet overflow is to have enough receive room for at least 2 maximum packets, i.e.
    • fullWMMark = (rxScheduledBuffers x rxBuffSize) / TCPIP_EMAC_MAX_FRAME - (2 x TCPIP_EMAC_MAX_FRAME ) / rxBuffSize;
    • Always TCPIP_EMAC_FLOW_CONTROL_FULL_WMARK > TCPIP_EMAC_FLOW_CONTROL_EMPTY_WMARK
    • Used only when auto flow control is enabled
    • Adjust to your own value
    • Default value should use the calculation of the watermark based on the selected RX sizes and buffers:
      • TCPIP_EMAC_FLOW_CONTROL_FULL_WMARK = ((TCPIP_EMAC_RX_DEDICATED_BUFFERS * TCPIP_EMAC_RX_BUFF_SIZE) / TCPIP_EMAC_MAX_FRAME - (2 x TCPIP_EMAC_MAX_FRAME ) / TCPIP_EMAC_RX_BUFF_SIZE)
    • Default value: 2
    • Symbol TCPIP_EMAC_FLOW_CONTROL_FULL_WMARK

  • The Empty Water Mark, in Number of Packets:

    • An 8 bit value representing the empty water mark, in number of packets
    • When the auto flow control is active and the number of pending received packets falls reaching this threshold the auto flow control pause frames will stop
    • Always TCPIP_EMAC_FLOW_CONTROL_FULL_WMARK > TCPIP_EMAC_FLOW_CONTROL_EMPTY_WMARK
    • Used only when auto flow control is enabled
    • Default value could be 0: resume normal traffic when there is no pending RX packet
    • Default value: 0
    • Symbol TCPIP_EMAC_FLOW_CONTROL_EMPTY_WMARK

  • External PHY Device:

    • The external PHY connected to the MAC device
    • Default value: ""
    • Symbol DRV_INTMAC_PHY_TYPE

  • ETHMAC Heap Size (bytes):

    • Estimation of the heap size taken by the MAC driver
    • Default value: none
    • Symbol DRV_ETHMAC_HEAP_SIZE