中文版
Description
Output refresh stage: When all instructions are executed, the on-off state of the output status
register is sent to the output latches in the output refresh stage, and is output through a certain
formula (relay, transistor or thyristor) to drive the corresponding output device to work. The PLC
initially developed and produced is mainly used to replace the traditional control device composed of
relay contactors, but the operation mode of the two is not the same:
ABB DSAI 135
(1) The relay control device uses a hard logic to run in parallel, that is, if the coil of the relay is powered
on or off, all the contacts of the relay (including its normally open or normally closed contacts) will immediately
and simultaneously operate on the position of the relay control line.
(2) The CPU of the PLC adopts the operation mode of sequential logic scanning the user program, that is, if an
output coil or logic coil is switched on or disconnected, all the contacts of the coil (including its normally open or
normally closed contacts) will not act immediately, and must wait until the contact is scanned. In order to eliminate
the differences caused by different modes of operation between the two, considering that the action time of various
types of contacts of the relay control device is generally more than 100ms, and the time of PLC scanning user programs
is generally less than 100ms, so the PLC adopts a scanning technology that is different from the general micro computer.
In this way, in the case of low I/O response requirements, there is no difference in the processing results of PLC and relay control devices.
Please contact Sunny sales@xiongbagk.cn for the best price.
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➱ email mailto: sales@xiongbagk.cn
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