Setting Minimum Data Transfer Rate; Setting The Read Termination Pattern - HP 9000 Series 300 Tutorials Manual

Setting Minimum Data Transfer Rate
DIL provides a means for specifying a minimum acceptable data transfer rate
for a given interface special file within the limits of available hardware by use
of io_speed_ctl. The calling sequence is as follows:
io_speed_ctl(eid, speed);
where eid is the entity identifier for the open interface file, speed is an integer
indicating a minimum speed in Kbytes per second, and a kilobyte equals 1 024
bytes.
Io_speed_ctl returns a 0 if successful, or -1 if an error occurred. For
example:
requests a minimum speed of 1 024 bytes per second. While the system may
use a faster transfer rate if possible, you are at assured that the rate will not be
less than the specified speed.
The transfer method (such as DMA or interrupt) chosen by the system is
determined by the minimum speed requested. The system selects a transfer
method that is as fast or faster than the requested speed. If the requested
speed is beyond system limitations, the fastest available transfer method is
used. Refer to the appropriate hardware-specific appendix for details.
Setting the Read Termination Pattern
During read operations on an open device file, the system recognizes certain
conditions as the end of a data transfer from the sending device. DIL supports
three methods for identifying the end of an input operation:
• Input data byte count limit is reached.
• Hardware condition is used to identify end of data.
• Predetermined character or sequence of characters is used to identify
the end of a data record.
Input termination occurs when the first termination condition is recognized,
independent of the type of condition. If two or more conditions occur
simultaneously, the first condition detected terminates the operation. However,
this first condition along with any other simultaneous events that would also
General-Purpose Routines 2-19