Specifications
Operat ion
Page
62
The third stage is to load the "operating system". This could
actually be any type of program. The load procedure
is
the same as
for the tertiary loader, except that the final message
is
a transfer
address and parameters. The transfer address and parameters are
passed up to the higher level with the notification of successful
completion. Also, the final message is acknowledged with a request
memory for the next segment, which the assistant understands as an
acknowledgement rather than a request.
During the second and third stages, the
Dump/Load Requester keeps a
timer while waiting for a message from the assistant. If this timer
runs out, the
Dump/Load Requester declares the load
as
failed with a
"failed" error return. This timer
is
set according to the service-
timer for the particular data link.
Also during the second and third stages, the loaders must not accept a
Memory Load with Transfer Address message with any memory image in
it.
This is to avoid confusion with additional secondary loaders received
in response to the primary loader.
4.3
Loop Test
This section describes the operation of the Loop Test Server and
Requester for point-to-point channels. The operation for multicast
channels is the Ethernet standard, found in Appendix
E
or Version
2.0
of the Ethernet Specification.
The operational descriptions assume the following Loop Test protocol
messages.
.
Looped Data
-
a message identifiable as a response to some
request.
.
Loop Data
-
a message that is to be looped to its sender.
4.3.1 Loop Server
The Loop Server always keeps a receive pending for each channel that
is turned on. Whenever a receive completes, it is processed and
another receive posted. For purposes of not missing messages, it may
be necessary to keep more than one receive posted.
The received message is processed according to function code:
.
Loop Data message: The function
code
is
changed to Looped Data
and the message is transmitted back to the source system.
.
Unrecognized function code: The message is ignored.