PLC实现控制的过程一般是：
输入刷新--再运行用户程序--再输出刷新--再输入刷新--再运行用户程序--再输出刷新……永不停止地循环反复地进行着。
有了上述过程，用PLC实现控制显然是可能的。因为：有了输入刷新，可把输入电路监控得到的输入信息存入PLC的输入映射区；经运行用户程序，输出映射区将得到变换后的信息；再经输出刷新，输出锁存器将反映输出映射区的状态，并通过输出电路产生相应的输出。又由于这个过程是永不停止地循环反复地进行着，所以，输出总是反映输入的变化的。只是响应的时间上，略有滞后。当然，这个滞后不宜太大，否则，所实现的控制不那么及时，也就失去控制的意义。
为此，PLC的工作速度要快。速度快、执行指令时间短，是PLC实现控制的基础。事实上，它的速度是很快的，执行一条指令，多的几微秒、几十微秒，少的才零点几，或零点零几微秒。而且这个速度还在不断提高中。
公共处理工作有：循环时间监控、外设服务及通讯处理等。
监控循环时间的目的是避免"死循环"，避免程序不能反复不断地重复执行。办法是用"看门狗"（Watchingdog）。只要循环超时，它可报警，或作相应处理.
外设服务是让PLC可接受编程器对它的操作，或通过接口向输出设备如打印机输出数据.
ENI DCG- 200
ENI DCG- 200
ENI MKS DC POWER SUPPLY DCG-100A
ENI DCG-200
ENI MKS DCG-200Z
DCG-200Z DC22S-Z022000010A
ENI DCG-200
MKS ENI DCG-100
ENI DCG-100
ENI MKS DCG-200ZHC-S02
ENI DCG-200Z
ENI DCG-200Z
ENI DCG-100A DCG4M-A001101010
ENI DCG-100A DC26M-Z011100010C
ENI DCG-100A DCG2M-A001200020C
ENI DCG-100A DCG2M-A001200020MA
ENI DCG-200Z DC21M-Z041300110A
07KT97
FCP270 P0917YZ
FBM233 P0926GX
Kuka KSD1-64
TRICONEX系统AI端子板 9771-210
TRICONEX系统DI端子板 9563-810
TRICONEX系统DO端子板 9662-810
TRICONEX系统PI端子板 9853-610
INDRAMAT MDD090B-N-040-N2M-110GL1
INDRAMAT MDD090B-N-040-N2M-110GL1
INDRAMAT MDD090C-N-040-N2M-110GR1
INDRAMAT MDD090C-N-040-N2M-110GB0
INDRAMAT MAC071C-0-JS-2-C/095-A-0
A20B-0008-0242
A20B-8100-0144
A16B-2200-0092
A02B-0259-B501
LOGANSPORT S60793-AA
A06B-6088-H222#H500
ABB 264DCFBDFSSSA4A1V2E4N2
INDRAMAT KDS1.1-100-300-115
A16B-2200-0760
INDRAMAT 4-050-300-W1-000
FANUC A06B-0143-B075#7000
FANUC A06B-0147-B084#7008
FANUC A06B-0143-B088#7000
FANUC A06B-0143-B084#7075
FANUC A06B-0143-B077#7075
FANUC A06B-0128-B575#7008
ABB 1FT3074-5AZ21-9-Z
FANUC A06B-0128-B688#7076
INDRAMAT MDD090C-N-030-N2L-110GB0
INDRAMAT MDD071C-N-030-N2S-095PA0
AB 1391-DES45-DI-AQB
AB 2706-B21J8
AB 800T-1T2
MODICON MM-PM10300C
CUTLER D72WN0P7646DW98
MODICON AS-506P-F16
MODICON 91-01538-05
MODICON M110-0144
AB 1771-P2
A16B-2201-0580
A16B-2200-0121
A16B-1200-0744
A16B-2201-0103
MODICON AS-PDAP-209
RELIANCE P56H3161S-XX
RELIANCE P56H3003R
DAYTON 3N350C
MARATHON M330
DAYTRONIC 9305A
ABB 3HAB4039-1/6
MODICON AS-B883-200 -13
MODICON AS-B883-201
AB 1361-D063-Z-5-10
AB 1785-L30B/E
AB 1771-IFE
KEPTROL KP8A3A2E
MODICON AS-B231-501
MARATHON FDM121-4.8
MODICON AS-B805-016
MODICON AS-884A-211
MODICON S76D-E01-F010
MODICON AS-B230-501
MODICON AS-B275-501
AB 1771-0BDC
MODICON PC-0984-480
AB 8J213THTS8864ANP147I
AB 2711-KC1
AB 1772-LWPD
FANUC A06B-0128-B575#7008
MODICON AS-521P-111
AB 38-K21ILC-01
AB 871C-C5A18
AB 802M-K1Y12NF
MODICON AS-P484-600
AB 871C-K2A12
MODICON AS-B885-002
AB 1771-OAD
AB 1746-IA16
MODICON AS-B833-16
MODICON AS-P420-000
RELIANCE P56H7213PBD
MODICON AS-BDEP-218
MODICON AS-BDAP-218 ）
AB 1326AB-A3E-11
AB 8000-IOAB
AB 1772-LXD
AB 13365-EN5
AB SLM-90037642
AB 1771-IGC
AB 1326AB-C4C-11-A7
AB 1326AB-C3E-11-A7
AB 8000-KA
AB 1771-ASC
AB 1772-LG
AB 1326AB-C4C-11
AB 160-BMB2
AB 1326AB-B520F-21-K5
AB 8520-CRTC1
AB 1771-KA2
AB 1771-IB
A06B-0143-B077#7075
AB 1326AB-C2E-11
AB 8520-AA12
Foxboro CM902WM
Honewyell LSXM4N
AB 1773-L1A
AB 102931
Fuji A3603
16267-1/7 接口模块
ENI DCG- 200
ENI MKS DC POWER SUPPLY DCG-100A
ENI DCG-200
ENI MKS DCG-200Z
DCG-200Z DC22S-Z022000010A
ENI DCG-200
MKS ENI DCG-100
ENI DCG-100
ENI MKS DCG-200ZHC-S02
ENI DCG-200Z
ENI DCG-200Z
ENI DCG-100A DCG4M-A001101010
ENI DCG-100A DC26M-Z011100010C
ENI DCG-100A DCG2M-A001200020C
ENI DCG-100A DCG2M-A001200020MA
ENI DCG-200Z DC21M-Z041300110A
07KT97
FCP270 P0917YZ
FBM233 P0926GX
Kuka KSD1-64
TRICONEX系统AI端子板 9771-210
TRICONEX系统DI端子板 9563-810
TRICONEX系统DO端子板 9662-810
TRICONEX系统PI端子板 9853-610
INDRAMAT MDD090B-N-040-N2M-110GL1
INDRAMAT MDD090B-N-040-N2M-110GL1
INDRAMAT MDD090C-N-040-N2M-110GR1
INDRAMAT MDD090C-N-040-N2M-110GB0
INDRAMAT MAC071C-0-JS-2-C/095-A-0
A20B-0008-0242
A20B-8100-0144
A16B-2200-0092
A02B-0259-B501
LOGANSPORT S60793-AA
A06B-6088-H222#H500
ABB 264DCFBDFSSSA4A1V2E4N2
INDRAMAT KDS1.1-100-300-115
A16B-2200-0760
INDRAMAT 4-050-300-W1-000
FANUC A06B-0143-B075#7000
FANUC A06B-0147-B084#7008
FANUC A06B-0143-B088#7000
FANUC A06B-0143-B084#7075
FANUC A06B-0143-B077#7075
FANUC A06B-0128-B575#7008
ABB 1FT3074-5AZ21-9-Z
FANUC A06B-0128-B688#7076
INDRAMAT MDD090C-N-030-N2L-110GB0
INDRAMAT MDD071C-N-030-N2S-095PA0
AB 1391-DES45-DI-AQB
AB 2706-B21J8
AB 800T-1T2
MODICON MM-PM10300C
CUTLER D72WN0P7646DW98
MODICON AS-506P-F16
MODICON 91-01538-05
MODICON M110-0144
AB 1771-P2
A16B-2201-0580
A16B-2200-0121
A16B-1200-0744
A16B-2201-0103
MODICON AS-PDAP-209
RELIANCE P56H3161S-XX
RELIANCE P56H3003R
DAYTON 3N350C
MARATHON M330
DAYTRONIC 9305A
ABB 3HAB4039-1/6
MODICON AS-B883-200 -13
MODICON AS-B883-201
AB 1361-D063-Z-5-10
AB 1785-L30B/E
AB 1771-IFE
KEPTROL KP8A3A2E
MODICON AS-B231-501
MARATHON FDM121-4.8
MODICON AS-B805-016
MODICON AS-884A-211
MODICON S76D-E01-F010
MODICON AS-B230-501
MODICON AS-B275-501
AB 1771-0BDC
MODICON PC-0984-480
AB 8J213THTS8864ANP147I
AB 2711-KC1
AB 1772-LWPD
FANUC A06B-0128-B575#7008
MODICON AS-521P-111
AB 38-K21ILC-01
AB 871C-C5A18
AB 802M-K1Y12NF
MODICON AS-P484-600
AB 871C-K2A12
MODICON AS-B885-002
AB 1771-OAD
AB 1746-IA16
MODICON AS-B833-16
MODICON AS-P420-000
RELIANCE P56H7213PBD
MODICON AS-BDEP-218
MODICON AS-BDAP-218 ）
AB 1326AB-A3E-11
AB 8000-IOAB
AB 1772-LXD
AB 13365-EN5
AB SLM-90037642
AB 1771-IGC
AB 1326AB-C4C-11-A7
AB 1326AB-C3E-11-A7
AB 8000-KA
AB 1771-ASC
AB 1772-LG
AB 1326AB-C4C-11
AB 160-BMB2
AB 1326AB-B520F-21-K5
AB 8520-CRTC1
AB 1771-KA2
AB 1771-IB
A06B-0143-B077#7075
AB 1326AB-C2E-11
AB 8520-AA12
Foxboro CM902WM
Honewyell LSXM4N
AB 1773-L1A
AB 102931
Fuji A3603
16267-1/7 接口模块