EZ80F91MCU Datasheet, PDF (265/396 Pages) Zilog, Inc. – eZ80Acclaim-TM Flash Microcontrollers

eZ80F91 MCU
Product Specification
246
Offset
TWP
0000h
Descriptor
Table
0007h
Ethernet
Packet
Figure 49. Descriptor Table
The descriptor table contains three entries: the next pointer (NP), the packet size
(Pkt_Size) and the packet status (Stat), as illustrated in Figure 50.
TWP
NP
Pkt_Size
Stat
Offset
0000h
0003h
0005h
Figure 50. Descriptor Table Entries
NP is a 24-bit pointer to the start of the next packet. Pkt_Size contains the number
of bytes of data in the Ethernet packet, including the four CRC bytes, but does not
contain the seven descriptor table bytes. Stat contains the status of the packet.
Stat differs for Transmit and Receive packets. See Tables 134 and 135.
Table 134. Transmit Descriptor Status
Bit Name
15 TxOwner
14 TxAbort
13 TxBPA
Description
0 = Host (eZ80^®) owns, 1 = EMAC owns.
1 = Packet aborted (not transmitted).
1 = Back pressure applied.
PS019209-0504
PRELIMINARY
Ethernet Media Access Controller