User guide

DC 900-1338I 115
Chapter
7
Host/ICP Interface
Note
From the ICP’s perspective, the “host processor” can be either the
server processor of the Freeway in which the ICP resides, or the
processor of the client computer in which the ICP is embedded. In
this chapter, the terms “ICP host processor,” “ICP’s host,” and
“host/ICP interface” reflect this perspective.
This chapter describes the interface between the ICP’s host processor and an ICP. This
interface will be referred to as the “host/ICP interface.” It is managed by an XIO inter-
face which runs on the ICP, in the OS/Impact environment, and provides a queue-
driven, non-blocking interface to the host processor. Section 7.4 on page 135 gives
details of XIO.
7.1 ICP’s Host Interface Protocol
Communications between the ICP’s host and the ICPs is performed by the host’s
driver,
icp.c, and the ICP’s driver, XIO. Information concerning any data transfers
between the two is passed through a Protocol eXchange Region (PXR).
The PXR for the ICP6000 is implemented via a hardware device that has 16 byte wide
registers called mailboxes. The ICP’s host sees these registers as bytes on word bound-
aries, while the ICP sees them as consecutive bytes. One of these registers is used for
host-to-ICP commands; when the host writes to this register, an interrupt is generated