I/O Devices (Machine Signals); Central I/O Devices; Distributed I/O Devices - Siemens SINUMERIK 880 SW 6 Planning Manual

1 General Overview

1.4 I/O devices (machine signals)

1.4 I/O devices (machine signals)
Machine signals can be connected to the SINUMERIK 880 in the following ways:
• Connection to I/O modules in the central controller
• Connection to I/O submodules in the operator panel
• Connection of distributed I/O modules such as I/O modules in an expansion unit or DMP
submodules.
It is important to note that input signals of very short duration are either not detected by the
PLC or not passed on by the input modules to the PLC. There are two reasons for this:
• The PLC is a cyclic program. It therefore scans the inputs in cycles of a certain duration. If
an input signal is set and reset again between two scans, the signal change is not
detected by the PLC.
• Transfer from the distributed inputs/outputs is also cyclic because the stations exchange
signals with the PLC one after the other. If a signal is set and reset entirely within a cycle,
the signal change is not detected.
1.4.1

Central I/O devices

The I/O modules are inserted in the central controller. The signals are transferred to the I/O
area (PII, PIQ) according to the principles described in the "Provision of I/O signals, process
image" Section. The slightly different procedure when working with two PLCs is described in
the "Operation with two PLCs" Section (not with S5-155U).

1.4.2 Distributed I/O devices

The distributed I/O devices comprise I/O modules located in an expansion unit (EU) and DMP
submodules. An EU is required with the SINUMERIK 880 if:
• The I/O modules are to be installed in the vicinity of the machine in order to reduce the
amount of cabling
• The number of I/O modules to be used exceeds the number of slots available in the
central controller or
• If not only SINUMERIK I/O modules but also SIMATIC modules (see the Catalog for the
SINUMERIK 880) are to be used.
The assignment of input/output bytes to the distributed
machine peripherals is described in the Installation Instructions,
–––––––
1) If using a SIMATIC S5-155U, refer to SINUMERIK 880 with S5-155U, Difference Description to PLC 135 WB in
this context
1–34
Section 7.6.
© Siemens AG 1991 All Rights Reserved
01.93
1)
6ZB5 410-0HE02
SINUMERIK 880 (PJ)