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NT20S Internal Processing
Appendix E
S Number of words for screen element registration
The number of words used for screen element registration is as follows.
Allocated words: Number of words
Allocated bits : Number of words calculated by summing the number of bits in
each area and taking 1 word to be 16 bits.
[Example]
Character string memory tables: 3 of 12 allocated words each
Numeral memory tables : 4 of 2 allocated words each
Allocated bits for control : 19 I/O relays, 7 link relays (contiguous bits)
The number of words assigned to character string memory tables and numeral
memory tables is as follows:
12 words X 3 + 2 words X 4 = 44 words
The assignment for bits is as follows:
19 I/O relays B 16 = 1 word with a remainder of 3 bits ³ 2 words
7 link relays B 16 = 0 words with a remainder of 7 bits ³ 1 word
The total is therefore 44 words + 2 words + 1 word = 47 words
Elements occupying up to approximately 120 words, calculated in this way, can be
registered. If the number of elements is larger than this, internal processing is in-
creased in proportion to the excess number and this generates a delay in proces-
sing.
If the point where the registrable quantity is exceeded is in the middle of an ele-
ment that spans several words (for example a character string memory table), reg-
istration is quit without registering that element.
S Order of priority for registration
Elements are registered in the following order of priority according to their type.
(1) Allocated words of the PT status control area
(2) Allocated bits for control (lamps, touch switches)
(3) Allocated words of numeral memory tables
(4) Allocated words of character string memory tables
If there is more than one element for each of (2) through (4), the elements are reg-
istered in accordance with the following priority of word and bit areas:
(1) Data memory (DM)
(2) I/O relays (CH)
(3) Timers (TIM)
(4) Counters (CNT)
(5) Holding relays (HR)
(6) Auxiliary relays (AR)
Within each area, words and bits are allocated from the smallest number up.
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