Z183 EMAC Board
User Manual
13
UM008301-0401
Length
For a transmit operation, you must fill the Length of the frame, including DstAddr
and the last byte of data. For a received frame, the Length field contains the
number of bytes received, including DstAddr and four CRC bytes at the end of
frame. You must appropriately adjust the byte count.
DstAddr
For a transmit operation, DstAddr must contain the 48-bit destination EMAC
address that is sent over the wire. DstAddr[0] is the lowest 16 bits of the 48-bit
address. LSB (0) is sent out first. The D0 bit of DstAddr[0] identifies individual/
group addressing, per the 802.x standards.
In a receive operation, this field contains the destination address of the packet
and examining Flags indicates the Rx Filter criteria by which this packet has
been accepted by the MAC.
SrcAddr
For a transmit operation, the three-word (48-bit) SrcAddr field normally contains
the individual IEEE unique address assigned to the MAC at the time of
initialization or a protocol-dependent address assignment. See the Init8900()
function for more information.
FrmType
FrmType is either a length or type field, as determined by the protocol in
transmit and receive operations.
Payload
This field is the payload part of the frame that carries packet’s data content. The
“data” field may contain other types of packet envelopes with their own headers,
but it is considered data by the PHY layer that the driver operates. The data field
should not be more than 1,500 bytes for a transmit or receive operation.
