Operator`s manual

1-1
SECTION 1. FUNCTIONAL MODES
1.1 PROGRAM TABLES - *1, *2, AND *3
MODES
Data acquisition and processing functions are
controlled by instructions contained in program
tables. Programming can be separated into 2
tables, each having its own programmable
execution interval. A third table is available for
programming subroutines which may be called
by instructions in Tables 1 or 2 or by a special
interrupt. The *1 and *2 Modes are used to
access Tables 1 and 2. The *3 Mode is used to
access Subroutine Table 3.
When a program table is first entered, the
display shows the table number in the ID Field
and 00 in the Data Field. Press A and the 21X
will advance to the execution interval. If there is
an existing program in the table, enter an
instruction location number prior to A and the
21X will advance directly to the instruction (e.g.,
5 will advance to the fifth instruction in the
table).
1.1.1 EXECUTION INTERVAL
The execution interval is entered in units of
seconds as follows:
0.0125 .... 0.1 seconds, in multiples of 0.0125
0.1 .....6553 seconds, in multiples of 0.1 second
Intervals less than 0.1 second are allowed in
Table 1 only. Execution of the table is repeated
at the rate determined by this entry. The table
will not be executed if 0 is entered. Values less
than 0.1 are rounded to the nearest even
multiple of 0.0125. If the Interval is 0.1 or
greater, the 21X will not allow entry of digits
beyond 0.1.
The sample rate for a 21X measurement is the
rate at which the measurement instruction can
be executed (i.e., the measurement made,
scaled with the instruction's multiplier and offset,
and the result placed in Input Storage).
Additional processing requires extra time. The
throughput rate is the rate at which a
measurement can be made and the resulting
value stored in Final Storage. The maximum
throughput rate for fast single ended
measurements (other than with the burst
measurement) is 256 measurements per second
(16 measurements repeated 16 times per
second).
If the specified execution interval for a table is
less than the time required to process that table,
the 21X overruns the execution interval, finishes
processing the table and waits for the next
occurrence of the execution interval before
again initiating the table (i.e., when the
execution interval is up and the table is still
executing, that execution is skipped). Since no
advantage is gained in the rate of execution with
this situation, it should be avoided by specifying
an execution interval adequate for the table
processing time.
NOTE: Whenever an overrun
occurs, decimal points are displayed
on both sides of the sixth digit of the
21X display (e.g., L O.G. in the *0
Mode).
When the Output Flag is set high, extra time is
consumed by final output processing. The
execution interval may be exceeded at this time
only, which may be acceptable. For example,
suppose it is desired to measure every 0.1
seconds and output processed data every ten
minutes. The processing time of the table is
less than 0.1 seconds except when output
occurs (every 10 minutes). With final output
processing the time required is 1 second. With
the execution interval set at 0.1 seconds, and a
one second lag between samples once every 10
minutes, 10 measurements out of 6000 (.17%)
are missed: an acceptable statistical error for
most populations.
1.1.2 SUBROUTINES
Table 3 is used to enter subroutines which may
be called with Program Control Instructions in
Tables 1 and 2 or other subroutines. The group
of instructions which form a subroutine starts
with Instruction 85, Label Subroutine, and ends
with Instruction 95, End. (Section 12)