110672     IO: Serial Port I/O Handler  Version: January 1985
Submitted by: Ray Brownrigg, DSIR, Wellington, New Zealand
Operating System: RT-11 V4, V5.0, V5.1, TSX-PLUS V4.1  Source
Language: MACRO-11  Memory Required: 1.5KB  Hardware Required: Up to 8
extra serial interface ports, EIS Instructions.  Keywords: Data
Communications, Device Handlers
Abstract: The I/O handler is a renamed revision of the SP handler, the
major improvement being the use of a high-speed ring buffer.
This attempts to emulate the FIFO buffer to be found on a
multiplexor.  The rename is to avoid conflict with the RT-11
V5.1 spooler handler.
The handler provides for full duplex I/O on up to eight
serial interface ports at one time.  In particular, single
character transfers are possible, without the overhead of
multiple I/O requests, and without the need for privileged
mapping of the user program (which would provide access to
the I/O page).  Also important is the provision of high-speed
input to a TSX-PLUS program.
Two modes of operation are possible.  The output-only mode,
which uses the DC1/DC3 (X-ON/X-OFF) protocol, is invoked by a
keyboard COPY command, a FORTRAN WRITE statement, or a .WRITE
programmed request in MACRO.  The full duplex mode, for which
there are various protocol options, is available only through
the .SPFUN programmed request in MACRO.
At any one time, up to eight serial ports may be active,
performing either output or full duplex I/O, any one job may
be communicating with more than one serial port, and a number
of different jobs may be using the handler.  This multiple
job capability is particularly useful in RT-11XM and TSX-PLUS
A user manual and installation instuctions are included.
Assoc. Documentation: A technical report is available from the author.
This report
is not available from DECUS.
Restrictions: RT-11SJ must have device I/O timeout support enabled.
Media (Service Charge Code): One RX01 Diskette (KA)  Format: RT-11,
600' Magnetic Tape (MA)  Format: RT-11

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