Magic Packet Mode; Flow Control - Freescale Semiconductor MPC8313E Family Reference Manual

Enhanced Three-Speed Ethernet Controllers
The hash table cannot be used to reject frames that match a set of selected
addresses because unintended addresses can map to the same bit in the hash
table. The receive queue filer may be used to reject frames with unintended
address hits in the hash table.
15.6.2.8

Magic Packet Mode

eTSEC implements the AMD Magic Packet specification for LAN-initiated power management. This
mode is normally entered with the rest of the system in a low-power sleep mode. Software must enable
normal receive function in the Ethernet MAC, and then finally set the MACCFG2[MPEN] bit to enable
Magic Packet detection before the system enters a reduced mode. While the rest of the system is operating
in low-power mode, the enabled eTSEC continues to receive Ethernet frames, but discards them
immediately. Upon receipt of any frame whose contents contain the valid Magic Packet sequence, the
eTSEC exits out of Magic Packet mode, thus clearing MACCFG2[MPEN], and raises an error/diagnostic
interrupt through IEVENT[MAG], which causes the surrounding system to wake-up. Frames received
after Magic Packet mode has exited are received into software buffers as usual. Software can abort Magic
Packet mode by writing 0 to MACCFG2[MPEN] at any time.
AMD specify a Magic Packet to be any Ethernet frame containing a valid Ethernet header (Destination
and Source Addresses) and valid FCS (CRC-32), and whose payload includes the specific Magic Packet
byte sequence at any offset from the start of frame. The specific byte sequence comprises an unbroken
stream of 102 bytes, the first 6 bytes of which are 0xFFFFFF_FFFFFF, followed by 16 copies of the
MAC's unique IEEE station address in the normal byte order for Ethernet addresses. For example, if the
station address were 0x112233_445566, then the MAC would have to receive 0xFFFFFF_FFFFFF,
0x112233_445566, ..., 0x112233_445566 in any payload to detect a Magic Packet. Only frames addressed
specifically to the MAC's station address or a valid multicast or broadcast address can be examined for the
Magic Packet sequence.
15.6.2.9

Flow Control

Because collisions cannot occur in full-duplex mode, gigabit Ethernet can operate at the maximum rate. If
the rate becomes too fast for a station's receiver, the station's transmitter can send flow-control frames to
reduce the rate. Flow-control instructions are transferred by special frames of minimum frame size. The
length/type fields of these frames have a special value.
Table 15-144 lists the flow-control frame structure.
Size [Octets] Description
7
1
6 Destination address 01-80-C2-00-00-01 Multicast address reserved for use in MAC frames
6 Source address
2
MPC8313E PowerQUICC II Pro Integrated Processor Family Reference Manual, Rev. 3
15-154
Table 15-144. Flow Control Frame Structure
Value
Preamble
SFD
Length/type 88-08
NOTE
Start frame delimiter
(or MAC station address)
Control frame type
Comment
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