描述
PLC執(zhí)行程序的過程分為三個階段,即輸入采樣階段、程序執(zhí)行階段、輸出刷新階段,PLC的掃描工作過程:
(1)輸入采樣階段。在這一階段中,PLC以掃描方式讀入所有輸入端子上的輸入信號,并將各輸入狀態(tài)存入對應(yīng)的輸入映像寄存器中。此時,輸入映像寄存器被刷斷。在程序執(zhí)行階段和輸出刷新階段中,輸入映像存儲器與外界隔離,其內(nèi)容保持不變,直至下一個掃描周期的輸入掃描階段,才被重新讀入的輸入信號刷新??梢?,PLC在執(zhí)行程序和處理數(shù)據(jù)時,不直接使用現(xiàn)場當(dāng)時的輸入信號,而使用本次采樣時輸入到映像區(qū)中的數(shù)據(jù)。一般來說,輸入信號的寬度要大于一個掃描周期,否則可能造成信號的丟失。
(2)程序執(zhí)行階段。在執(zhí)行用戶程序過程中,PLC按照梯形圖程序掃描原則,一般來說,PLC按從左至右、從上到下的步驟逐個執(zhí)行程序。但遇到程序跳轉(zhuǎn)指令,則根據(jù)跳轉(zhuǎn)條件是否滿足來決定程序跳轉(zhuǎn)地址。程序執(zhí)行過程中,當(dāng)指令中涉及輸入、輸出狀態(tài)時,PLC就從輸入映像寄存器中“讀入”對應(yīng)輸入端子狀態(tài),從輸出映像寄存器“讀入”對應(yīng)元件(“軟繼電器”)的當(dāng)前狀態(tài)。然后進(jìn)行相應(yīng)的運算,運算結(jié)果再存入輸出映像寄存器中。對輸出映像寄存器來說,每一個元件(“軟繼電器”)的狀態(tài)會隨著程序執(zhí)行過程而變化。
(3)輸出刷新階段。程序執(zhí)行階段的運算結(jié)果被存入輸出映像區(qū),而不送到輸出端口上。在輸出刷新階段,PLC將輸出映像區(qū)中的輸出變量送入輸出鎖存器,然后由鎖存器通過輸出模塊產(chǎn)生本周期的控制輸出。如果內(nèi)部輸出繼電器的狀態(tài)為“1”,則輸出繼電器觸點閉合,經(jīng)過輸出端子驅(qū)動外部負(fù)載。全部輸出設(shè)備的狀態(tài)要保持一個掃描周期。
歐美品牌停產(chǎn)的,常用的“PLC”備品備件
我司產(chǎn)品應(yīng)用于以下領(lǐng)域:
1,《發(fā)電廠DCS監(jiān)控系統(tǒng)》
2,《智能平鋼化爐系統(tǒng)制造》
3,《PLC可編程輸送控制系統(tǒng)》
4,《DCS集散控制系統(tǒng)》
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5,《智能型消防供水控制系統(tǒng)》
6,《化工廠藥液恒流量計算機(jī)控制系統(tǒng)》
7,《電氣控制系統(tǒng)》造紙,印染生產(chǎn)線,變電站綜合自動化控制系列
本特利,英維思,伍德沃德,??怂共_、西屋、瑞恩、施耐德莫迪康、ABB、AB、西門子、摩托羅拉、GE發(fā)那科、安川、博世力士樂,ACSO,力士樂等各大品牌的DCS系統(tǒng)配件,機(jī)器人系統(tǒng)配件,大型伺服系統(tǒng)備件。
Woodward 5464-768 CPU-DCS II
Woodward 5464-827 CPU MODULE
Woodward 5464-828
Woodward 5464-829
Woodward 5464-830 A/I 4-20
Woodward 5464-833 4 ch
Woodward 5464-834
Woodward 5464-836 REMOTE XCVR
Woodward 5464-843 NetCon CPU Card
Woodward 5466-006 4-20mA Input
Woodward 5466-017 2 CH ACTUATOR DRIVER
Woodward 5466-026 DUPLEX CUR IN
Woodward 5466-031 Netcon I/O Controller?????
Woodward 5466-032 FTIO MODULE
Woodward 5466-033 CPU Module
Woodward 5466-041 2C Pos Control
Woodward 5466-042 CPU(GAP Compatible)-DCS
Woodward 5466-061 Module Master CPU
Woodward 5466-063 NetCon CPU Card
Woodward 5466-074 CPU Mod
Woodward 5466-250 netcon B FTIO
Woodward 5466-253 MPU A I/O
Woodward 5466-258 NetCon/MicroNet Discreet I/O Card 24/12
Woodward 5466-268
Woodward 5466-272 Solnd Mon
Woodward 5466-274 FTIO
Woodward 5466-315 NetCon/MicroNet Analog I/O Card
Woodward 5466-316 MPU A I/O
Woodward 5466-332 ANALOG I/O 24/8
Woodward 5466-336 SIO
Woodward 5466-340 Netcon F/O XCVR
Woodward 5466-348 Netcon 5000B SIO
Woodward 5466-351 Netcon CPU 040 with LLC Memory
Woodward 5466-352 CPU Module
Woodward 5466-353 MAIN XCVR
Woodward 5466-355 REMOTE XCVR
Woodward 5466-409 NetCon/MicroNet CPU Card
Woodward 5466-411 Ethernet Module(RJ45)
Woodward 5466-419 NT CPU
Woodward 5466-425 24/8A I/O
Woodward 5466-458
Woodward 5500-018
Woodward 5500-134 Ext.Card
Woodward 5500-159C 505 Relay Board
Woodward 5500-510
Woodward 5500-559 Buffer Board
Woodward 5500-563
Woodward 5501-003 Circuit Board for Peak 150
Woodward 5501-340
Woodward 5501-341
Woodward 5501-367 FTM(Field Termination)
Woodward 5501-376 FTM,ANALOG,HI DENS
Woodward 5501-411
Woodward 5501-428 2 CH ACTUATOR DRIVER
Woodward 5501-432 2 CH ACTUATOR DRIVER
Woodward 5501-465
Woodward 5501-466 MicroNet Power Supply
Woodward 5501-469 CPU LM6000 PC&PA
Woodward 5501-470 CPU_040 W/O LL?Memory??
Woodward 5501-471 NetCon/MicroNet SIO Card
Woodward 5501-510 FT Relay
Woodward 5503-173 MicroNet VME CPU Adapter
Woodward 5503-279 TC/RTD
Woodward 5503-282 FTM,analog
Woodward 5503-335 CPU
Woodward 6945-377 3103 Gas Fuel Valve
Woodward 8200-015 Peak 150(HVAC-No ModBus)
Woodward 8200-019 PEAK 150
Woodward 8200-177 DRIVER,EM DIGITAL/ANALOG
Woodward 8200-203 ProTech 203
Woodward 8200-226 SPC(servo position controller)
Woodward 8200-314 GS/LQ Digital Driver
Woodward 8220-805 Final Driver
Woodward 8226-043 OCP(operator control panel)
Woodward 8230-568 Control Panel
Woodward 8230-805 FINAL DRVR
Woodward 8230-815 HP Final Drive
Woodward 8230-827 LP Final Driver
Woodward 8230-840
Woodward 8230-841
Woodward 8230-896 Final Driver-Water
Woodward 8230-898 FINAL DRVR
Woodward 8234-167O 501 Chassie
Woodward 8234-213 Chassis-NetCon A
Woodward 8234-346A 501 Chassie
Woodward 8236-026
Woodward 8236-027 Operate Control Panel
Woodward 8236-039 OCP(operator control panel)
Woodward 8236-039 OCP(operator control panel)