12. Register Descriptions
272
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
MODE:
Determines if the image is used to generate Memory or IO commands on PCI. The MODE is
only applicable if the destination is the alternate PCI bus.
•
Memory Command Mode:
PCI Memory commands generated on PCI-2.
Bursting is supported.
PRKEEP and RD_AMT[2:0] are only applicable in Memory Command Mode.
•
IO Command Mode
Causes PCI IO commands to be generated on PCI-2. When the image is selected to perform IO
commands, transactions are limited to 4 bytes or less. A PCI Master initiated cycle attempting to
burst to the image in this mode will be terminated with a Target Disconnect (Retry) after every data
beat.
The MODE bit and the MEM_IO bit work together to control the size of the transaction (see
).
1011
128M
AD31-AD27
1100
256M
AD31-AD28
1101
512M
AD31-AD29
1110
1G
AD31-AD30
1111
2G
AD31
Table 68: Setting for MODE and MEM_IO Bits
MODE Setting
MEM_IO setting
Transaction size
0
X
a
a.
X means either 0 or 1.
Memory cycle (minimum
8 byte memory read)
1
0
I/O Cycle
1
1
Memory cycle (minimum
4 byte memory read)
Table 67: Block Size
BS[3:0]
Block Size
Address Lines Compared/Translated