User guide

7: Host/ICP Interface
DC 900-1338I 133
disposition flag in the header buffer to
FREE_BUF and the disposition flag in the data
buffer to
REL_BUF. Then, when the request is complete, the header buffer is marked
free by XIO, indicating to the task that it is available for re-use. The data buffer is
released to its partition by XIO, and requires no further processing.
If the disposition flag in either buffer is set to
POST_QE or POST_BUF, the correspond-
ing disposition modifier must contain a valid queue ID. If the requesting task is the
owner of the queue, it can suspend its operation and resume when XIO posts the queue
element or buffer (with a post and resume,
s_post, system call) to the queue on comple-
tion of the request.
If
FREE_QE or FREE_BUF is specified in the disposition flag of either buffer, the corre-
sponding disposition modifier should be set to a non-zero value so that the requesting
task can recognize the completion when the field is cleared by XIO.
7.2.4.2 Host Request Header Initialization
The subfunction, line number, and circuit number fields of the host request header are
defined for compatibility with other Simpact products and are not used for the ICP.
The function code must be set to one of the following values:
When a node is declared, a host read request queue ID and a host write request queue
ID are defined. For both the main and priority nodes, at least one host request queue
element containing a read function code (in the
funct field of the host request header)
must always be posted to that node’s read request queue, and a queue element contain-
ing a write function code must always be posted to that node’s write request queue.
For nodes specific to your ICP-resident task, at least one host request queue element
must always be posted to each node’s write request queue. For compatibility with other
0x02 = Write request
0x08 = Read request