Burst Transfers; Read Terminations; Determining Why A Read Operation Terminated; Specifying A Read Termination Pattern - HP 9000 Series 300 Tutorials Manual

Burst Transfers
Series 300 systems support high-speed burst I/O on HP-IB and GPIO
interfaces. The call to io_burst is structured as follows:
io_burst (eid, flag)
io_burst controls the data path between computer memory and the HP-IB or
GPIO interface. If flag
=
0, all data is handled through kernel calls with the
normal associated overhead. If flag is non-zero, burst mode locks the interface
and data is transferred directly between memory and the I/O mapped interface
until the transfer is completed. Burst mode yields substantial improvement in
efficiency when handling small amounts of data or high-speed data acquisition.
Read Terminations
Determining Why a Read Operation Terminated
Subroutine io_get_term_reason, described in Chapter 2, is used to determine
why the last read performed on a particular eid terminated. Possible reasons
include:
• The requested number of bytes were read
• A specified read termination character was seen
• A assertion of the PSTS line was seen
• Some abnormal condition occurred, such as an I/O timeout.
Specifying a Read Termination Pattern
Chapter 2 describes subroutine io_eol_ctl which is used to specify a
character or string of characters (called a read termination pattern) that, when
encountered during a read, terminates the read operation currently underway
on a particular GPIO interface file eid.
Interrupts
Subroutines io_on_interrupt and io_interrupt_ctl are described in
Chapter 2. They are used to set up and control interrupt handlers for the
GPIO status line or for a particular GPIO interface file eid.
Controlling the GPIO Interface 4-9