pnx1500 NXP Semiconductors, pnx1500 Datasheet - Page 696

• Manufacturer Part Number: pnx1500
• Description: Pnx15xx Series Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
4. Descriptor and Status Formats
PNX15XX_SER_3
Product data sheet
Figure 4:
Receive descriptor memory layout
RxDescriptorNumber
RxDescriptor
4.1 Receive Descriptors and Status
1
2
3
4
5
Table 3: PatternMatchJoin Register Nibble Functions
This section defines the descriptor format for the transmit and receive scatter/gather
DMA engines.
Each Ethernet packet can be broken into a set of fragments . Each fragment will have
a single corresponding descriptor. The DMA managers in the LAN100 can scatter (for
receive) and gather (for transmit) multiple fragments into a single Ethernet packet.
Figure 4
The receive descriptors are stored in an array in memory. The base address of the
array is stored in the RxDescriptor register. The number of descriptors in the array is
stored in the RxDescriptorNumber register using a minus-one encoding format. For
example, if the array has 8 elements, the RxDescriptorNumber register value should
Nibble (binary)
1011
1100
1101
1110
1111
b
b
b
b
b
depicts the layout of the receive descriptors in memory.
Control
Control
Control
Control
Control
Control
Packet
Packet
Packet
Packet
Packet
Packet
Name
b
!a
!b
0
1
Rev. 3 — 17 March 2006
Chapter 23: LAN100 — Ethernet Media Access Controller
Data Buffer
Data Buffer
Data Buffer
Data Buffer
Data Buffer
Data Buffer
Function
Feedthrough b
Invert a
Invert b
Fix match output to zero
Fix match output to one
RxStatus
…Continued
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
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PNX15xx Series
StatusInfo
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