2. PCI Interface
65
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
The Inbound MFAs are 32-bit offsets from the translated PowerSpan II I
2
0 target image window base
address in local IOP memory. When the Host platform or an external IOP wishes to send a message to
the local IOP it must first obtain an MFA from the Inbound Free List. The external platform is then free
to place a message in the associated MF. The MFA is then placed into the Inbound Post List for the
Local IOP to process.
2.6.3.3
Outbound Queue
The Outbound Queue Register is the messaging interface used by the local IOP to post messages to the
Host. The I
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O Outbound Queue Register Interface is located at offset 0x044 of the PowerSpan II PCI
I
2
O target image in PCI memory space. The Outbound Queue has a Free List FIFO and a Post List
FIFO, both of which reside in the IOP local memory. The Free List contains the Message Frame
Address (MFAs) of Message Frames (MFs) in the Host system memory, which are available to the
local IOP for writing outbound messages. Outbound MFAs are absolute addresses of a Message Frame
in Host memory. The Post List contains the MFAs of MFs in the Host system memory which contain
outbound messages for the Host to process. When the local IOP wishes to send a message to the Host
platform it must first obtain an MFA from the Outbound Free List. The local IOP is then free to place a
message in the associated MF. The MFA is then placed into the Outbound Post List for the Host to
process. All Outbound messages are targeted for the Host platform. If the local IOP wishes to send a
message to another IOP (peer-to-peer communication) it uses the external IOPs Inbound Queue to post
the Message.
2.6.3.4
Protocol for Exchanging Messages
PowerSpan II I
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O Registers
The PowerSpan II PCI I
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O Shell Interface implements the following I
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O defined registers:
•
I
2
O Outbound Post List Interrupt Status Register
•
I
2
O Outbound Post List Interrupt Mask Register
•
I
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O Inbound Queue
•
I
2
O Outbound Queue
•
I
2
O Host Outbound Index Register (used for Outbound Option)
In addition to the registers defined in the
I
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O 2.0 Specification
, PowerSpan II implements a number of
registers to support the I
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O message passing protocol of the Shell Interface.
•
PCI I
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O Target Image Control Register (PCI_TI2O_ CTL)
•
PCI I
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O Target Image Translation Address Register (PCI_TI2O_ TADDR)
•
I
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O Queue Base Address Register (I20_ QUEUE_BS)
All I
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O Inbound Queue MFAs must be offsets of greater than 4 Kbytes.