12. Register Descriptions
257
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
12.5.5
PCI-1 I2O Target Image Base Address Register
This register specifies the 64 KByte aligned base address of the device’s PCI I
2
O Target Image in PCI
Memory space. PowerSpan II only supports the I
2
O Target Image on the Primary PCI Interface.
The first 4 Kbytes of this image provides the I
2
O Shell Interface Inbound and Outbound Queues and the
Host Interrupt Status and Mask Registers. Cycles claimed by the PowerSpan II I
2
O Target Image with
offsets greater than 4 Kbytes is passed on to the Processor Bus. The control information for the
PowerSpan II I
2
O Target Image is fully defined in the PCI_TI2O_CTL and PCI_TI2O_TADDR registers.
A write must occur to this register before the device’s I
2
O Target Image is accessed through PCI Memory
transactions. This write can be performed with either a PCI configuration transaction or a register access
by the local processor.
A Base Address of 0x00000 is not a supported base address and the register image does not respond to
PCI transactions as a target device when 0x00000 is written to this field — the image is disabled.
PowerSpan II supports a Base Address of 0x00000 if the BAR_EQ_0 bit is set in the
Control and Status Register” on page 318
.
The BS field in the
“PCI I2O Target Image Control Register” on page 352
determines the size of the
image requested in PCI Memory space for the PCI I
2
O Target Image.
Writes are enabled to this register only if the BAR_EN bit in the PCI_TI2O_CTL register is set.
This register is not implemented in the Secondary PCI Interface.
Register Name: P1_BSI2O
Register Offset: 0x010
PCI
Bits
Function
PB
Bits
31-24
BA
0-7
23-16
BA
8-15
15-08
0
0
0
0
0
0
0
0
16-23
07-00
0
0
0
0
PRFTCH
TYPE
SPACE
24-31
Name
Type
Reset
By
Reset
State
Function
BA[15:0]
R/W
P1_RST
0
Base Address
PRFTCH
R/WPB
P1_RST
1
EEPROM
Prefetchable
Memory is prefetchable
TYPE [1:0]
R
P1_RST
0
Type
00 = locate anywhere in 32-bit address space
SPACE
R
P1_RST
0
PCI Bus Address Space
0 = Memory