PCVisionplus
Hardware Reference
Registers
3–81
Rev 02; February 8, 2002
3.5.12 Scatter Gather Table (DPDATA) R/W
0
7
BADR3 + 0x80000–0xBFFFC
DPDATA7
DPDATA6
DPDATA5
DPDATA4
DPDATA3
DPDATA2
DPDATA1
DPDATA0
8
15
DPDATA15
DPDATA14
DPDATA13
DPDATA12
DPDATA11
DPDATA10
DPDATA9
DPDATA8
DPDATA
16
23
DPDATA23
DPDATA22
DPDATA21
DPATAT20
DPDATA19
DPDATA18
DPDATA17
DPDATA16
24
31
DPDATA31
DPDATA30
DPDATA29
DPDATA28
DPDATA27
DPDATA26
DPDATA25
DPDATA24
The Bus Master Controller uses the scatter gather table to define a destination buffer for bus master transfers to the
PCI-bus. The table contains destination pointers. Each pointer takes two DWORD locations in the scatter gather
table. The even addresses contain PCI-bus destination addresses. The odd addresses contain transfer count values.
The Segment Size register (SGSZ) defines how many of these destination pointers are used in a bus master transfer
operation. The DMASTART address in the BMCTLX register define the first destination pointer used for a data
transfer. Once the BMEN bit is set, the BMC loads the Transfer Count and Destination Address information form the
Scatter Gather Table and sends data to the host buffer defined.
0x80000
DSTADR 0
32-bit destination start address
0x80004
XCNT 0
transfer count
0x80008
DSTADR 1
32-bit destination start address
0x8000C
XCNT 1
transfer count
. . .
. . .
0xBFFF8
DSTADR 32767
32-bit destination start address
0xBFFFC
XCNT 32767
transfer count
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