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5-20

Installing Remote Base Controllers—RBCs SIMATIC 545/555/575 System Manual

PPX:505–6870 RBC (continued)

The RESET pushbutton on the front of the RBC is deliberately recessed to

prevent accidental activation. When you press this button, a global reset is

immediately performed on the RBC. After completing reset, the RBC

assumes the RS-232 baud rate stipulated by the setting of switches 1

through 3 on the dipswitch, and the station address indicated by switches 4

through 10.

WARNING

Pressing the RESET button when the system is operating causes the RBC to be

logged off the system. When the RBC is logged off, inputs and outputs

associated with the base are affected, as described below. If you do not take the

condition of your inputs and outputs into account, logging the RBC off the

system can cause unpredictable process operation.

Unpredictable process operation can cause death or serious injury to

personnel, and/or damage to equipment.

Do not reset your RBC unless you understand and are prepared for the

consequences (described below).

The following actions take place when an RBC is reset.

• The CPU logs the RBC off the system and sets the image register

points which represent the inputs from this RBC’s base to zero. The

image register is zeroed out until the RBC completes reset and resumes

communication with the CPU. If this occurs while the system is

operating, depending on your RLL program, turning these inputs off

could affect other base outputs.

• From the assertion of reset until the RBC completes the reset and

resumes communication with the CPU, the state of the outputs on this

RBC’s base is determined by the output module, with no reference to

the RBC’s E1 (Off/Freeze) jumper. Discrete outputs go off (to a value of

zero). Analog/word outputs obey their own Zero/Hold Last Value

selection. If no Zero/Hold Last Value selection is available on the

module, the analog/word outputs hold their last value.

• If the station address you assign to the RBC (by setting the dipswitch)

inadvertently duplicates an address already in use by a second slave on

the I/O channel, then when the RBC completes its reset and attempts

to communicate, identifying itself with the new station address, the

second slave may be logged off the system. Intermittent operation could

occur as long as the two slaves are set to the same station address.

Reset Pushbutton

Resetting the RBC

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