(二) 用户程序履行时期
在用户程序履行时期，PLC老是按由上而下的次第顺次地扫描用户程序(梯形图)。在扫描每一条梯形图时，又老是先扫描梯形图左边的由各触点构成的操控线路，并按先左后右、先上后下的次第对由触点构成的操控线路进行逻辑运算，然后依据逻辑运算的成果，改写该逻辑线圈在体系RAM存储区中对应位的状况；或许改写该输出线圈在I/O映象区中对应位的状况；或许断定是不是要履行该梯形图所规则的特别功用指令。

即，在用户程序履行进程中，只需输入点在I/O映象区内的状况和数据不会发作改变，而别的输出点和软设备在I/O映象区或体系RAM存储区内的状况和数据都有也许发作改变，并且排在上面的梯形图，其程序履行成果会对排在下面的凡是用到这些线圈或数据的梯形图起作用；相反，排在下面的梯形图，其被改写的逻辑线圈的状况或数据只能到下一个扫描周期才干对排在其上面的程序起作用。

(三) 输出改写时期
当扫描用户程序完毕后，PLC就进入输出改写时期。在此时期，CPU依照I/O映象区内对应的状况和数据改写一切的输出锁存电路，再经输出电路驱动相应的外设。这时，才是PLC的真实输出

同样的若干条梯形图，其摆放次第不一样，履行的成果也不一样。别的，选用扫描用户程序的运转成果与继电器操控设备的硬逻辑并行运转的成果有所区别。当然，假如扫描周期所占用的时刻对全部运转来说能够疏忽，那么二者之间就没有什么区别了。

ABB 900060  DDR Switch cable
ABB 3HAB2136-1  Teach pendant S3
ABB 3HAB2151-1  Teach pendant S3
ABB 3HAB2477-1  Floppy drive S2/S3
ABB 3HAB2480-1  Floppy drive S4
ABB 3HAB5386-1  Teach pendant S4
ABB 3HAC14441-9  CMOS-battery
ABB 3HNE00311-1  Teach pendant S4C
ABB 3HNE00313-1  Teach pendant S4C
ABB 4944016-2  Battery S3
ABB 4944026-2  Battery memory board S2
ABB YB161100-LH  Teach pendant S2
ABB YB560100-EA  Teach pendant S3
ABB YB560101-LA  Power supply
ABB YT212002-BA  Rectifier
ABB YT212002-C  Rectifier
ABB YT212002-X  Rectifier
ABB YB560103-CB DSQC236B DriveUnit
ABB YB560103-CC DSQC236C DriveUnit
ABB 3HAB2207-1 DSQC236D DriveUnit
ABB YB560103-CD DSQC236G DriveUnit
ABB 3HAB2207-1 DSQC236P DriveUnit
ABB YB560103-CE DSQC236T DriveUnit
ABB YB560 103-CL/5 DSQC241 PowerUnit
ABB 3HAB 2210-1 DSQC300 Robot Computer
ABB 3HAB 2216-1 DSQC314B PowerUnit
ABB 3HAB 2219-1 DSQC316 Main Computer
ABB 3HAB 2220-1 DSQC317 6MB Card
ABB 3HAB 2236-1 DSQC321 4MB Card
ABB 3HAB 5956-1 DSQC323 8MB Card
ABB 3HAB 5957-1 DSQC324 16MB Card
ABB 3HAB 2241-1 DSQC325 Main Computer
ABB 3HAB 2242-1 DSQC326 Robot Computer
ABB 3HAB7229-1 DSQC328 I/O Card
ABB 3HAB 6182-1 DSQC335 Robot Computer
ABB 3HAB8101-3/05D DSQC345B DriveUnit
ABB 3HAB8101-3/08C DSQC345C DriveUnit
ABB 3HAB8101-7/01C DSQC346C DriveUnit
ABB 3HAB8101-8 DSQC346G DriveUnit
ABB cable DSQC351 Interbus-S
ABB 3HAC 0373-1 DSQC361 Main Computer
ABB 3HAC3180-1 DSQC373 Robot Computer
ABB 900054 1Gb SD-card S3/S4 DDR
ABB 900056 1Gb SD-card S2 DDR
3HNE 00026 Teach Pendant
3HNE 00312-1 Teach Pendant
3HNE 00313 Teach Pendant
CHAA 3560-AXA Teach Pendant
ABB 3HAB9271-1/01B DriveUnit Dummy DriveUnit Dummy
ABB 57510001-AA DSCA 114 Print out board
ABB 57520001-U DSCA 121 Communication board
ABB 57160001-A DSDI 110 Digital input board
ABB 57160001-K DSDO 110 Digital output board
ABB YB161102-AH DSDX 110 Digital in/output board
ABB 57160001-TP DSDX B001 digital in-output board
ABB 57360001-U DSMB 124 Semiconductor memory board
ABB 57360001-AN DSMB 125 Semiconductor memory board
ABB 57360001-HG DSMB 127 Memory board
ABB 57330001-N DSMC 110 Floppy disk controller
ABB YB161102-AK DSPA 110 Axis computer
ABB 57310256-AF DSPC 150 Central processor
ABB 57310256-BA DSPC 153 Expand. single board computer
ABB 57310001-GP DSPC 157 Expand. single board computer
ABB YB161102-AD DSQC 103 Resolver power board
ABB YB161102-AF DSQC 105 Display board
ABB YB161102-BA DSQC 110 Programming board
ABB YB161102-BS DSQC 115 Resolver power board + 2 analogue
ABB YB161102-BE DSQC 116 Power supply
ABB YB161102-BG DSQC 117 Resolver power board
ABB YB161102-BU DSQC 124 Terminal unit
ABB YB161102-BV DSQC 129 R/D board
ABB YB161102-CH DSQC 136 Safety board
ABB YB161102-CM DSQC 138 Terminal unit
ABB YB560103-AC DSQC 202 Robot computer
ABB YB560103-AS DSQC 208A External axis board
ABB YB560103-AL DSQC 209 Analogue I/O board
ABB YB560103-AM DSQC 210 Safety board
ABB YB560103-AN DSQC 211 Power supply
ABB YB560103-BF DSQC 215 Robot computer
ABB YB560103-AZ DSQC 220 Programming board
ABB YB560103-BD DSQC 223 PC Board digital I/O
ABB YB560103-BE DSQC 224 PC Board combi I/O
ABB YB560103-BK DSQC 227 Winchester interface
ABB YB560103-BD DSQC 228 Safety board
ABB YB560103-BN DSQC 230 Robot computer
ABB YB560103-BS DSQC 233 External axis board
ABB YB560103-BY DSQC 235A Rectifier
ABB YB560103-BZ DSQC 235B Rectifier
ABB YB560103-CA DSQC 236A Drive unit
DSQC 236B Drive
ABB YB560103-CC DSQC 236C Drive unit
ABB 3HAB2207-1 DSQC 236D Drive unit
ABB YB560103-CD DSQC 236G Drive unit
ABB 3HAB2245-1 DSQC 236H Drive unit
ABB 3HAA3563-AJA DSQC 236P Drive unit
ABB YB560103-CE DSQC 236T Drive unit
DSQC 239 Board - ABB RIO
ABB  DSQC 241 Power supply
ABB YB560103-CM DSQC 242 Programming board