UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 163 of 841
NXP Semiconductors
UM10360
Chapter 10: LPC176x/5x Ethernet
The transmit number of descriptors register defines the number of descriptors in the
descriptor array for which TxDescriptor 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.
10.12.11 Transmit Produce Index Register (TxProduceIndex - 0x5000 0128)
The Transmit Produce Index register (TxProduceIndex) has an address of 0x5000 0128.
Its bit definition is shown in Table 158
.
The transmit produce index register defines the descriptor that is going to be filled next by
the software transmit driver. The transmit descriptor array is empty as long as
TxProduceIndex equals TxConsumeIndex. If the transmit hardware is enabled, it will start
transmitting frames as soon as the descriptor array is not empty. After a frame has been
processed by software, it should increment the TxProduceIndex. The value must be
wrapped to 0 once the value of TxDescriptorNumber has been reached. If the
TxProduceIndex equals TxConsumeIndex - 1 the descriptor array is full and software
should stop producing new descriptors until hardware has transmitted some frames and
updated the TxConsumeIndex.
10.12.12 Transmit Consume Index Register (TxConsumeIndex - 0x5000 012C)
The Transmit Consume Index register (TxConsumeIndex) is a read-only register with an
address of 0x5000 012C. Its bit definition is shown in Table 159
.
The transmit consume index register defines the descriptor that is going to be transmitted
next by the hardware transmit process. After a frame has been transmitted hardware
increments the index, wrapping the value to 0 once the value of TxDescriptorNumber has
been reached. If the TxConsumeIndex equals TxProduceIndex the descriptor array is
empty and the transmit channel will stop transmitting until software produces new
descriptors.
10.12.13 Transmit Status Vector 0 Register (TSV0 - 0x5000 0158)
The Transmit Status Vector 0 register (TSV0) is a read-only register with an address of
0x5000 0158. The transmit status vector registers store the most recent transmit status
returned by the MAC. Since the status vector consists of more than 4 bytes, status is
Table 158. Transmit Produce Index register (TxProduceIndex - address 0x5000 0128) bit
description
Bit Symbol Function Reset
value
15:0 TxProduceIndex Index of the descriptor that is going to be filled next by the
transmit software driver.
0x0
31:16 - Unused 0x0
Table 159. Transmit Consume Index register (TxConsumeIndex - address 0x5000 012C) bit
description
Bit Symbol Function Reset
value
15:0 TxConsumeIndex Index of the descriptor that is going to be transmitted next by
the transmit datapath.
0x0
31:16 - Unused 0x0
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