Rockwell-automation 1772-LP3 PLC - 2/30 Programmable Controller Progra Uživatelský manuál stáhnout pdf (Strana 111)

Timer and Counter Instructions

Chapter 5

513

Figure 5.10

UpDown

Counter Example

||

(

CTU )

110 046

PR 220

AC 1

||

( CTD )

110 046

PR 220

AC 1

||

( CTR )

110 046

PR 220

AC 1

UpCount Event

DownCount Event

Counter Reset Event

NOTE: Bit 14 of the Accumulated Value word is set on when the

Accumulated Value either overflows or underflows. When a

Down-Counter Preset is set to 000, underflow bit 14 is not set on when the

count goes below zero.

When used alone, the CTD accumulated value may need to be reset in the

program to its original value (usually a value other than 000). For this

reason, a Get/Put transfer (Section 6.1), rather than a CTR instruction, is

usually used to load a value in the CTD Accumulated Value word. Get/Put

instructions are discussed in Section 6.1.

This output instruction is similar to a standard counter instruction. During

a true rung condition, the Accumulated Value is incremented once per

program scan (Figure 5.11). Unlike counters, however, the scan counter

does not count past the preset and resets when the rung goes false, power is

lost or the keyswitch is turned to program mode.

Figure 5.11

Scan

Counter Instruction

||

( SCT )

113 053

PR 700

AC 359

5.2.4

Scan Counter Instruction

1 2 ... 106 107 108 109 110 111 112 113 114 115 116 ... 345 346

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