12. Register Descriptions
360
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
12.5.65
I2O Queue Base Address Register
This register specifies the location and size of the Inbound and Outbound Queues in processor memory
space. The IOP must program this register before enabling the PowerSpan II I2O Shell Interface.
FIFO_SIZE:
This field specifies the size of the circular FIFOs in the IOP local memory. Total FIFO
memory allocation is four times the single FIFO size (see
).
Register Name: I2O_QUEUE_BS
Register Offset: 0x50C
PCI
Bits
Function
PB
Bits
31-24
PB_I2O_BS
0-7
23-16
PB_I2O_BS
PowerSpan II Reserved
8-15
15-08
PowerSpan II Reserved
16-23
07-00
PowerSpan II Reserved
FIFO_SIZE
24-31
I2O_QUEUE_BS Description
Name
Type
Reset
By
Reset
State
Function
PB_I2O_BS
[11:0]
R/W
PRI_RST
0
Processor Bus I2O Base Address
The PB_I2O_BS field specifies the base address of the
1 MB block of embedded PowerPC memory that
contains the four FIFOs (Inbound Free List, Inbound
Post List, Outbound Free List, Outbound Post List).
The four FIFOs are of equal size, but do not need to be
in contiguous memory locations. The PB_I2O_BS field
is aliased in the most significant 12 bits of each of the
PowerSpan II I2O Bottom and Top Pointer Registers.
FIFO_SIZE [2:0]
R/W
PRI_RST
0
FIFO Size
This field specifies the size of the circular FIFOs in the
IOP local memory. Total FIFO memory allocation is
four times the single FIFO size (see
Table 85: I2O FIFO Sizes
FIFO_SIZE [2:0]
Maximum Number of
MFAs per FIFO
Memory Required per
FIFO (Kbytes)
PowerSpan II I2O Pointer
bits incremented
a
000
256
1
I2O_PTR [9:2]
001
1K
4
I2O_PTR [11:2]
010
4K
16
I2O_PTR [13:2]