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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
132 of 808
NXP Semiconductors
UM10360
Chapter 10: LPC17xx Ethernet
12.9 Transmit Status Base Address Register (TxStatus - 0x5000 0120)
The Transmit Status base address register (TxStatus) has an address of 0x5000 0120. Its
bit definition is shown in
.
The transmit status 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 statuses.
12.10 Transmit Number of Descriptors Register (TxDescriptorNumber -
0x5000 0124)
The Transmit Number of Descriptors register (TxDescriptorNumber) has an address of
0x5000 0124. Its bit definition is shown in
.
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.
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
.
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
Table 134. Transmit Status Base Address register (TxStatus - address 0x5000 0120) bit
description
Bit
Symbol
Function
Reset
value
1:0
-
Fixed to ’00’
-
31:2
TxStatus
MSBs of transmit status base address.
0x0
Table 135. Transmit Number of Descriptors register (TxDescriptorNumber - address
0x5000 0124) bit description
Bit
Symbol
Function
Reset
value
15:0
TxDescriptorNumber
Number of descriptors in the descriptor array for which
TxDescriptor is the base address. The register is minus
one encoded.
31:16
-
Unused
0x0
Table 136. 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