LM3S8G62 Datasheet, PDF (810/1096 Pages) Texas Instruments – Stellaris® LM3S8G62 Microcontroller

Ethernet Controller
OBSOLETE: TI has discontinued production of this device.
Table 17-2. Ethernet Signals (108BGA) (continued)
Pin Name
Pin Number Pin Mux / Pin Pin Type Buffer Type^a Description
Assignment
XTALPPHY
J2
fixed
I
Analog Ethernet PHY XTALP 25-MHz oscillator crystal
input or external clock reference input.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
17.3
Functional Description
Note: A 12.4-kΩ resistor should be connected between the ERBIAS and ground. The 12.4-kΩ
resistor should have a 1% tolerance and should be located in close proximity to the ERBIAS
pin. Power dissipation in the resistor is low, so a chip resistor of any geometry may be used.
The functional description of the Ethernet Controller is discussed in the following sections.
17.3.1
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 and reception options, and LED indicators.
17.3.1.1
Ethernet Frame Format
Ethernet data is carried by Ethernet frames. The basic frame format is shown in Figure
17-3 on page 810.
Figure 17-3. Ethernet Frame
Preamble
7
Bytes
SFD Destination Address
Source Address
Length/
Type
1
Byte
6
Bytes
6
Bytes
2
Bytes
Data
46 - 1500
Bytes
FCS
4
Bytes
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 17-3 on page 812) of the DA determines whether the address is an
individual (0), or group/multicast (1) address.
■ Source Address (SA)
The source address field identifies the station from which the frame was initiated.
■ Length/Type Field
810
July 24, 2012
Texas Instruments-Production Data