Alspa C80-35 24 Vdc Input, Neg/Pos Logic, 1 ms ... - GE Fanuc PLC

Chapter2System OperationThis chapter describes certain system operations of the Alspa C80–35 PLC, Alspa C80–25 PLC and C80–05 MicroPLCs. These system operations include: A summary of PLC sweep sequences (see § 1.). Program organization and user references/data (see § 2.). Power–up and power–down sequences (see § 3.). Clocks and timers (see § 4.). System security through password assignment (see § 5.). Model 35 I/O modules (see § 6.). Model 25 and Micro I/O (see § 6.).1. PLC SWEEP SUMMARYThe logic program in the Alspa C80–35, Alspa C80–25 and Micro PLCs execute repeatedly until stopped by acommand from the programmer or a command from another device. The sequence of operations necessary toexecute a program one time is called a sweep. In addition to executing the logic program, the sweep includesobtaining data from input devices, sending data to output devices, performing internal housekeeping, servicingthe programmer and servicing other communications.The Alspa C80–35, Alspa C80–25 and Micro PLCs normally operate in Standard Program Sweep mode. Otheroperating modes include STOP with I/O Disabled mode, STOP with I/O Enabled mode, and Constant Sweep mode.Each of these modes, described in this chapter, is controlled by external events and application configurationsettings. The PLC makes the decision regarding its operating mode at the start of every sweep.ALS 52102 c–en Alspa C80–35, C80–25 and C80–05 PLCs Reference ManualPage 2–1