HP 3000 III Series Manual page 267

i.
j.
k.
1.
m.
I/O System
If the character on the ICS is a data character, it is trans-
ferred (9) by TIP to the terminal buffer. If it is a control
character, TIP performs the appropriate control function.
TIP exits (10) to the Dispatcher and the sequence repeats
back to step g until the entire record has been read.
When a CR (Carriage Return) control character is detected,
TIP sets a flag in the DIT to signify that the record is
complete, then causes the Term inal Monitor to be executed
( 11) .
The Terminal Monitor transfers the content of the terminal
buffer to the user stack (12) and the transmission log in the
I
CQ
is updated.
The Terminal Monitor releases the line buffer and control is
returned to the user process (13). To read another record,
the file system must make another I/O request to Attach I/O.
1-8. Direct Write
The sequence
figure 7-7.
of operations for direct write is illustrated
The sequence of operations is as follows:
in
a. The executing user process generates a file request (1, fig-
ure 7-7) in the file system.
b. The file system tests the validity of the request and calls
the Attach I/O intrinsic (2).
c. Attach I/O inserts the request parameters (3)
Queue for the requested device.
in the I/O
d. When all higher priority requests have been completed, the
Terminal Monitor begins execution for this request (4).
e. The Terminal Monitor transfers the data (5) from the data
buffer to the line buffer.
f. A CIa instruction (6) is issued to the Device Controller to
initiate the write operation.
g. The Device Conroller causes the CPU to interrupt to TIP (7).
h. TIP transfers a character (8) to the ICS.
i. TIP executes a WIO instruction, transferring the character
(9) from the ICS to the Device Controller.
j. TIP then exi ts to the Dispatcher (10), and hardware takes
control.
k. The Device Controller writes the character (11) out to the
device.
7-13