User Manual

UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved.
User manual Rev. 2 — 19 August 2010 160 of 840
NXP Semiconductors
UM10360
Chapter 10: LPC17xx Ethernet
The receive number of descriptors register defines the number of descriptors in the
descriptor array for which RxDescriptor is the base address. The number of descriptors
should match the number of statuses. The register uses minus one encoding i.e. if the
array has 8 elements, the value in the register should be 7.
10.12.6 Receive Produce Index Register (RxProduceIndex - 0x5000 0114)
The Receive Produce Index register (RxProduceIndex) is a read-only register with an
address of 0x5000 0114. Its bit definition is shown in Table 153
.
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.
10.12.7 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 Table 154
.
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
Table 152. Receive Number of Descriptors register (RxDescriptor - address 0x5000 0110) bit
description
Bit Symbol Function Reset
value
15:0 RxDescriptorNumber Number of descriptors in the descriptor array for which
RxDescriptor is the base address. The number of
descriptors is minus one encoded.
0x0
31:16 - Unused 0x0
Table 153. 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 154. 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