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
184
Section 7: DMA
Document
1250_1125-UM100CB-R
D
ATA
M
OVER
C
ONTROL
R
EGISTERS
Table 114: Data Mover Descriptor Base Address Register
dm_dscr_base_0 -
00_1002_0B00
dm_dscr_base_1 -
00_1002_0B20
dm_dscr_base_2 -
00_1002_0B40
dm_dscr_base_3 -
00_1002_0B60
Read clears some bits
Bits
Name
Default
Description
3:0
zero
4'b0
These bits must be zero.
39:4
base
36'bx
This is the base address of the descriptor ring.
55:40
ring_size
16'bx
This field sets the total number of descriptors in the ring. If this field is set to 0 the ring
will contain 65536 descriptors.
58:56
priority
3'bx
This field gives the weight for this channel. It sets how many descriptors are processed
from this channel before advancing round robin to the next channel.
000: 1 descriptor.
001: 2 descriptors.
010: 4 descriptors.
011: 8 descriptors.
100: 16 descriptors.
101-111: Reserved
59
active
1'b0
Read Only. This bit is set when a descriptor from the current channel is actively being
used. When the enbl bit is cleared the channel will remain enabled until this bit is clear.
60
interrupt
1'b0
Read Only. This bit is set when the channel is interrupting because of the end of a transfer
with the descriptor interrupt bit set. This bit is cleared by a read from the
dm_dscr_base
register.
61 error
(R/O)
reset (W/O)
1'b0
On a read this bit is set when the channel is interrupting because of a data transfer error
(uncorrectable ECC, Bus Error or Fatal bus error signalled on the D_CODE). If such an
error occurs the channel will abort. This bit is cleared by a read from the
dm_dscr_base
register.
If this bit is written with a 1 the current descriptor pointer is reset to the base address of
the descriptor ring (bits 39:0). This should always be done the first time a channel is
enabled.
62
abort(W/O)
1'b0
If this bit is written with a 1 the DMA engine will abort the current transfer and disable the
channel. If both this bit and the enbl bit (bit 63) are set in the same write, this bit will
override and the channel will be aborted.
63
enbl
1'b0
This bit must be set to enable the DMA channel. If this bit is cleared while the channel
is running the current transfer is completed before the engine stops. (Use the abort bit
to cause the engine to stop immediately).
Table 115: Debug Data Mover Descriptor Base Address Register
dm_debug_dscr_base_0 -
00_1002_0B18
dm_debug_dscr_base_1 -
00_1002_0B38
dm_debug_dscr_base_2 -
00_1002_0B58
dm_debug_dscr_base_3 -
00_1002_0B78
READ ONLY
Bits
Name
Description
63:0
dscr_base Reading from this register gives the same data as reading from the
dm_dscr_base
register
(
), but without the side effect of clearing the interrupt and error status bits. It is intended for
debugger access to the status.
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