An object is a monitored, named Logix variable, with a "value" which
may be accessed and altered.  The object is created by either of the
macro calls:

    object(<logix_variable>)
    object(<initial value>, <logix_variable>)

where <initial value> is an arbitrary Logix term; if <initial value>
is omitted, the initial value of the object is integer 0.  The
<logix_variable> is instantiated as a result of the call.

An <object_call> (see Spifcp/BNF.txt) presents a request to the monitor.
It has the form:

    <logix_variable> ! <object_request>

The requests are:

    close(<request_reply>)
    name(<logix_variable>, <request_reply>)
    read(<logix_variable>, <request_reply>)
    store(<logix_term>, <request_reply>)
    values(<logix_variable>, <request_reply>)

The <request_reply> may be omitted; in that case the close request is
just the string "close".

The <logix_variable> is instantiated by the request to the appropriate
value:

    name	The name of the object.
    read	The most recent value of the object.
    values	A Logix list of values stored to the object, beginning
		with the most recent one.  Note that the tail of the
		list is uninstantiated until the object is closed.

In response to the store request, the monitor notes the <logix_term>
as the most recent value of the object, and unifies it with a trailing
list element.

An object may appear in place of a <weighter_parameter>.  In that
case, the most recent value of the object is used to compute the value
of the <weighter_declaration>.


There is one predefined object, SPITIME, which may be referenced by:

    SPITIME ! read(Value)

to obtain the current value of the internal clock, or by:

    SPITIME ! values(List)

to obtain a list of values of the internal clock, starting with its
current value.  This list may be viewed as a stream which is augmented
each time a transmission is completed.

The internal clock is a positive, increasing, real number, initially 0.

The 'close' and 'store' commands are not permitted for this object.


The object monitor is implemented by spi_object.cp .  The 


This document is licensed under Gnu General Public License - Version 3

    http://www.nongnu.org/efcp/gnu-gpl3.html