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# 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