Campbell Scientific CR10 CR10 Measurement and Control - Page 158

SECTION 12. PROGRAM CONTROL INSTRUCTIONS PARAM. DATA NUMBER ryPE 01: 2 DESCRIPTION Subroutine number (1-9, 79-99) *** g6 DO *** FUNCTION This Instruction unconditionally executes the specified command. PARAM. DATA NUMBER TYPE DESCRIPTION 01: 2 Command (Table 12-2) *** 87 LOOP *** FUNCTION Instructions included between the Loop Instruction and the End lnstruction (95) are repeated the number of times specified by the iteration count (Parameter 2), or until an Exit Loop command (31,32) is executed by a Program Control Instruction within the Loop. lf 0 is entered for the count, the loop is repeated until an Exit Loop command is executed. The first parameter, delay, controls how frequently passes through the loop are made. Its units are multiples of the table execution interval. A delay of 0 means that there is no delay between passes through the loop. Each time the table is executed all iterations of the loop will be completed and execution will pass on to the following instructions. lf the delay is 5, every fifth time that the execution interval comes up, one pass through the loop is made; only those instructions in the loop will be executed and other portions of the table are not executed in the interim. When a loop with delay is executed. the next execution stafts at the loop, skipping over any previous and following instructions in the table. When a fixed number of iterations are executed, the time spent in the loop is equalto the product of the execution interval; delay, and the number of iterations. For example, a loop with a delay of 1 and a count of 5 will take 5 seconds if the execution interval is 1 second. When the loop is first entered, one pass through the loop is made, then the CR10 delays untilthe next execution intervaland makes the second pass through the loop. After making the fifth pass through the loop, there is the fifth delay, 12-2 after which execution passes to the instruction following the END instruction which goes with the loop. While in a loop with delay, the table will not be initiated at each execution interval. (However, the overrun decimals will not be displayed.) Some consequences of this are: The Output Flag will not be automatically cleared between passes through the loop. Because Table 2 cannot interrupt Table 1, Table 2 will not be executed while Table 1 is in a loop with delay. Table 1 will not interrupt Table 2 in the middle an output array. Thus, if the Output Flag is set in Table 2prior to enteringthe loop orwithin the loop, the flag must be specifically cleared ,the end of the pass if Table 1 is to be executed. Input locations for Processing lnstructions a loop can be entered as Indexed locations. An Indexed location causes the input location to be incremented by 1 with each pass through the loop. (The Index counter is added to the location number in the program table.) Input locations which are not indexed will remain constant. To specify an Indexed location, depress the C key at some point while keying in the digits for the input location and before entering the location with the A key. Two dashes, --, appear in the two right most characters of the display, indicating the entry is Indexed. When the same output processing is required on values in sequential input locations, it must be accomplished by using the repetitions parameter of the Output lnstruction, not by indexing the input location within a loop. An Output Instruction within a loop is allotted the same number of Intermediate Storage locations as it would receive if it were not in the loop. For example, the average instruction with a single repetition is allotted only two Intermediate locations: one for the number of samples and one for the running total. Each time through the loop the sample counter is incremented and the value in the referenced input location is added to the total. lf the input location is indexed, the values from all input locations are added to the same total. Note that if the Output Flag is set prior to entering the loop in the above example, 10 values will be output. The first will be the