Preamble
SFD Destination Address
Source Address
Length/
Type
FCS
Data
7
Bytes
6
Bytes
6
Bytes
2
Bytes
1
Byte
4
Bytes
46 -1500
Bytes
MACRIS
MACIACK
MACIM
Interrupt
Control
MACRCTL
MACNP
Receive
Control
MACTCTL
MACTHR
MACTR
Transmit
Control
Transmit
FIFO
Receive
FIFO
MACIA0
MACIA1
Individual
Address
MACMCTL
MACMDV
MII
Control
MACDDATA
Data
Access
MACTS
Timer
Support
MACMTXD
MACMRXD
Interrupt
Functional Description
1382
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Ethernet Media Access Controller (EMAC)
Figure 19-2. Ethernet MAC Block Diagram
19.3 Functional Description
The functional description of the EMAC is discussed in the following sections.
19.3.1 MAC Operation
The following sections describe the operation of the MAC layer, including an overview of the Ethernet
frame format, the MAC layer FIFOs, Ethernet transmission, reception options, packet timestamps, and
Ethernet MAC address format.
19.3.1.1 Ethernet Frame Format
Ethernet data is carried by Ethernet frames. The basic frame format is shown in
.
Figure 19-3. Ethernet Frame
The seven fields of the frame are transmitted from left to right. The bits within the frame are transmitted
from least to most significant bit.
•
Preamble
The Preamble field is used to synchronize with the received frame’s timing. The preamble is 7 octets
long.
•
Start Frame Delimiter (SFD)
The SFD field follows the preamble pattern and indicates the start of the frame. Its value is
1010.1011b.
•
Destination Address (DA)
This field specifies destination addresses for which the frame is intended. The LSB (bit 16 of DA oct 1
in the frame, see Table 18-3 on page 907) of the DA determines whether the address is an individual
(0), or group/multicast (1) address.