UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
706 of 1269
NXP Semiconductors
UM10503
Chapter 26: LPC43xx Ethernet
26.6.28 DMA Transmit poll demand register
The Transmit Poll Demand register enables the Transmit DMA to check whether or not the
current descriptor is owned by DMA. The Transmit Poll Demand command is given to
wake up the TxDMA if it is in Suspend mode. The TxDMA can go into Suspend mode due
to an Underflow error in a transmitted frame or due to the unavailability of descriptors
owned by Transmit DMA. You can give this command anytime and the TxDMA will reset
this command once it starts re-fetching the current descriptor from host memory.
25
AAL
Address-aligned beats
When this bit is set high and the FB bit equals 1, the AHB interface generates all
bursts aligned to the start address LS bits. If the FB bit equals 0, the first burst
(accessing the data buffer’s start address) is not aligned, but subsequent bursts are
aligned to the address.
0
R/W
26
MB
Mixed burst
When this bit is set high and FB bit is low, the AHB master interface will start all bursts
of length more than 16 with INCR (undefined burst) whereas it will revert to fixed burst
transfers (INCRx and SINGLE) for burst-length of 16 and below.
0
R/W
27
TXPR
When set, this bit indicates that the transmit DMA has higher priority than the
receive DMA during arbitration for the system-side bus.
0
R/W
31:28
-
Reserved
0
RO
Table 560. DMA Bus mode register (DMA_BUS_MODE, address 0x4001 1000) bit description
…continued
Bit
Symbol
Description
Reset
value
Access
Table 561. Programmable burst length settings
Data bus width
FIFO depth
Valid PBL range in full duplex
mode
32 bit
128 bytes
8 or less
256 bytes
32 or less
512 bytes
64 or less
1 kB
128 or less
2 kB and above
all
Table 562. DMA Transmit poll demand register (DMA_TRANS_POLL_DEMAND, address
0x4001 1004) bit description
Bit
Symbol
Description
Reset
value
Access
31:0
TPD
Transmit poll demand
This register field can be read by the application, and when
a write operation is performed with any data value, an event
is triggered.
When these bits are written with any value, the DMA reads
the current descriptor pointed to by the Current Host
Transmit Descriptor register (
). If that
descriptor is not available (owned by Host), transmission
returns to the Suspend state and bit 2 in the DMA_STAT
Register is asserted. If the descriptor is available,
transmission resumes.
0
R/W