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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
156 of 808
NXP Semiconductors
UM10360
Chapter 10: LPC17xx Ethernet
All of the above interrupts can be enabled and disabled by setting or resetting the
corresponding bits in the IntEnable register. Enabling or disabling does not affect the
IntStatus register contents, only the propagation of the interrupt status to the CPU (via the
NVIC).
The interrupts, either of individual frames or of the whole list, are a good means of
communication between the DMA manager and the device driver, triggering the device
driver to inspect the status words of descriptors that have been processed.
Transmit example
illustrates the transmit process in an example transmitting uses a frame
header of 8 bytes and a frame payload of 12 bytes.
After reset the values of the DMA registers will be zero. During initialization the device
driver will allocate the descriptor and status array in memory. In this example, an array of
four descriptors is allocated; the array is 4x2x4 bytes and aligned on a 4 byte address
boundary. Since the number of descriptors matches the number of statuses the status
array consists of four elements; the array is 4x1x4 bytes and aligned on a 4 byte address
boundary. The device driver writes the base address of the descriptor array
(0x2008 10EC) to the TxDescriptor register and the base address of the status array
Fig 19. Transmit example memory and registers
StatusInfo
StatusInfo
StatusInfo
StatusInfo
Packet
0x20081314
TxStatus
0x200811F8
TxDescriptor
0x200810EC
0x200810EC
0x200810F0
0x200810F4
0x200810F8
0x200810FC
0x20081100
0x20081104
0x20081108
0x200811F8
0x200811FC
0x20081200
0x20081204
Packet
0x20081411
Packet
0x20081419
Packet
0x20081324
descriptor array
d
es
c
ri
pt
or
0
des
cr
ipt
or
1
de
sc
ri
pt
or
2
d
es
c
ri
pt
or
3
des
cr
ipt
or
ar
ray
fragment buffers
TxProduceIndex
TxConsumeIndex
TxDescriptorNumber
= 3
sta
tu
s 1
sta
tu
s 0
st
a
tu
s 3
st
a
tu
s 2
st
at
us
ar
ray
status array
PACKET 1 HEADER (8 bytes)
PACKET 0 PAYLOAD (12 bytes)
PACKET 0 HEADER (8 bytes)
0 0
7
Control
CONTROL
0 0
7
Control
CONTROL
1 1
3
Control
CONTROL
0 0
7
Control
CONTROL
0x2008131
4
0x2008131
B
0x20081411
0x20081419
0x2008141C
0x20081324
0x2008132B