Systerr:-Level Operation - HP 3000 Series Installation And Service Manual

Principles of Operation
LS I de vices, ( 10) 'I1he data comm device that is being used
serializes the data and sends it over the line, (11) , effect-
ively completing the initialization cf data transm issicr:.
The INP initiates the data reception function by initializing the
mC'.dem cont.rel lines to indicate that data can be received. It
then begins monitcring the communication line for a start-of-
message sequence.
Having initialized the transmission and reception of data, the
INf' Micrcprocessor now performs functiom; such as mana_ging
special characters in the data stream, calculating and comparing
CH Cs, tr a m; f e r r in
g b 1
oc ks t o and fr om the HP 3 0
0 0 ,
and
man
a g in
g
rnc·cem
signals.
When an end-of-message sequence is detected, the CPC is calcu-
lated and checked. If there is no error, the message is accepted
and transferred tc the HP 3000. The INP returns to its task of
mcnitcring the line for the next start-of-message sequence.
Terminating the transmission sequence involves sending the neces-
sary end-of-message information and changing the appropriate
modem control lines to indicate the end cf transmission.
4-9. SYSTEM-LEVEL OPERATION
The f0llowing discussion demonstrates the functioning of an INF
at thE· system level. A very basic DS/3000 example is given here,
but INP usage with other data communications subsystems (such as
RJE, MRJE, etc.) can easily be construed.
IUP operation begins with the system operator opening the DSLINE
I
(by means of the :DSCONTROL console command). At this time the
INP hardware logic is reset and the ROM-resident verification
test (SELF TEST) is invoked. Upon the successful completion of
SELF TEST, the respective communications line protocol software
is downloaded to the INP RAH. The HP 3000 then commands the INP
software to begin execution.
The software initializes itself to conform to the DSLINE as con-
figured on the mainframe. At this time, a read command is issued
to the INP, so that messages coming from the remote computer
through the data communications line can be received. When a
1-:-iessage is received from the remote computer, the local HP 3000
is notified (and data is moved to the mainframe RAM) only at
successful completion of the read.
Closing the DSLilJE causes any current INP - to - HP 3000 messages
to be completed. The INP then becomes dormant until the
next :DSCONTROL command.
JUN 1980
4-5
I