BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
164
Section 7: DMA
Document
1250_1125-UM100CB-R
47:32
high_watermark 16'b0
This specifies the high watermark for generating an interrupt to the CPU based on
the number of descriptors.
If the MAC receiver is asserting flow control and the number of descriptors rises
above this watermark it will remove the flow control.
63:48
low_watermark
16'b0
This specifies the low watermark for generating an interrupt to the CPU based on
the number of descriptors.
The MAC receiver will assert flow control when the number of descriptors falls
below this watermark.
Table 91: Ethernet and Serial DMA Configuration Register 0
(Cont.)
Table 92: Ethernet and Serial DMA Configuration Register 1
dma_config1_mac_0_rx_ch_0 -
00_1006_4808
dma_config1_mac_0_tx_ch_0 -
00_1006_4C08
dma_config1_mac_0_rx_ch_1 -
00_1006_4908
dma_config1_mac_0_tx_ch_1 -
00_1006_4D08
dma_config1_mac_1_rx_ch_0 -
00_1006_5808
dma_config1_mac_1_tx_ch_0 -
00_1006_5C08
dma_config1_mac_1_rx_ch_1 -
00_1006_5908
dma_config1_mac_1_tx_ch_1 -
00_1006_5D08
dma_config1_mac_2_rx_ch_0 -
00_1006_6808
dma_config1_mac_2_tx_ch_0 -
00_1006_6C08
dma_config1_mac_2_rx_ch_1 -
00_1006_6908
dma_config1_mac_2_tx_ch_1 -
00_1006_6D08
dma_config1_ser_0_rx -
00_1006_0408
dma_config1_ser_0_tx -
00_1006_0488
dma_config1_ser_1_rx -
00_1006_0808
dma_config1_ser_1_tx -
00_1006_0888
Bits
Name
Default
Description
0
hdr_cf_en
1'b0
If this bit is set then the L2_cacheable bit will be asserted during header
transfers to cause the L2 cache to be allocated.
1
asic_xfr_en
1'b0
Set to enable special support for transferring packets to an ASIC on the
HyperTransport fabric (or PCI bus).
2
pre_addr_en
1'b0
Set when asic_xfr_en is set to enable prepending of the DMA descriptor to the
packet sent to the ASIC.
3
flow_ctl_en
1'b0
Set to cause the controller to send a flow control request to the interface when
the descriptor count falls below the low watermark, and only remove the
request when the count goes above the high watermark. MAC receive
channels only, setting this bit in other channels causes UNDEFINED behavior.
4
no_dscr_updt
1'b0
Set to prevent the descriptor being written with the status at the end of a packet
transfer, saving bandwidth through the bridge. (Transmit channels only.)
5
dscr_l2ca
1'b0
This bit sets the L2 cacheability for descriptors. If it is set the L2CA bit will be
set in descriptor requests, causing them to be cached in the L2 cache. If clear
the descriptors will not be allocated in the L2 on a miss.
6 (rx)
xtra_status
(tx) cpu_pause_en
1'b0
Ethernet Receive channels only: This bit should only be set for the Ethernet
receive engine and only if the system revision indicates PERIPH_REV3 or
greater. If this bit is set the a_size field will be overwritten with additional status
information in the start of packet descriptor.
Ethernet Transmit channels only: This bit should only be set for the Ethernet
transmit engine and only if the system revision indicates PERIPH_REV3 or
greater. If this bit is set the channel will pause at the end of the current packet
and will resume only when the bit is cleared.
7
fc_pause_en
1'b0
Ethernet Transmit channels only: This bit should only be set for the Ethernet
transmit engine and only if the system revision indicatess PERIPH_REV3 or
greater. If this bit is set and the interface is set for DMA channel based flow
control (ch_base_fc_en bit set in the
mac_vlantag
register) then this channel
will be paused by a flow control frame, if this bit is clear and the interface is set
for DMA channel based flow control the channel will not be paused by a flow
control frame. If the interface is not configured for DMA channel based flow
control this bit is ignored.
15:8 reserved 8'b0
Reserved
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