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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
131 of 808
NXP Semiconductors
UM10360
Chapter 10: LPC17xx Ethernet
The receive produce index register defines the descriptor that is going to be filled next by
the hardware receive process. After a frame has been received, hardware increments the
index. The value is wrapped to 0 once the value of RxDescriptorNumber has been
reached. If the RxProduceIndex equals RxConsumeIndex - 1, the array is full and any
further frames being received will cause a buffer overrun error.
12.7 Receive Consume Index Register (RxConsumeIndex - 0x5000 0118)
The Receive consume index register (RxConsumeIndex) has an address of 0x5000 0118.
Its bit definition is shown in
.
The receive consume register defines the descriptor that is going to be processed next by
the software receive driver. The receive array is empty as long as RxProduceIndex equals
RxConsumeIndex. As soon as the array is not empty, software can process the frame
pointed to by RxConsumeIndex. After a frame has been processed by software, software
should increment the RxConsumeIndex. The value must be wrapped to 0 once the value
of RxDescriptorNumber has been reached. If the RxProduceIndex equals
RxConsumeIndex - 1, the array is full and any further frames being received will cause a
buffer overrun error.
12.8 Transmit Descriptor Base Address Register (TxDescriptor -
0x5000 011C)
The Transmit Descriptor base address register (TxDescriptor) has an address of
0x5000 011C. Its bit definition is shown in
.
The transmit descriptor base address is a byte address aligned to a word boundary i.e.
LSB 1:0 are fixed to “00”. The register contains the lowest address in the array of
descriptors.
Table 131. Receive Produce Index register (RxProduceIndex - address 0x5000 0114) bit
description
Bit
Symbol
Function
Reset
value
15:0
RxProduceIndex Index of the descriptor that is going to be filled next by the
receive datapath.
0x0
31:16
-
Unused
0x0
Table 132. Receive Consume Index register (RxConsumeIndex - address 0x5000 0118) bit
description
Bit
Symbol
Function
Reset
value
15:0
RxConsumeIndex Index of the descriptor that is going to be processed next by
the receive
31:16
-
Unused
0x0
Table 133. Transmit Descriptor Base Address register (TxDescriptor - address 0x5000 011C)
bit description
Bit
Symbol
Function
Reset
value
1:0
-
Fixed to ’00’
-
31:2
TxDescriptor
MSBs of transmit descriptor base address.
0x0