American Audio VELOCITY - REV 4-05 Betriebsanleitung PDF herunterladen (Seite 167)

METRO RAIL DESIGN CRITERIA SECTION 9 / SYSTEMS

Appendix A

DE304.09 Appendix 9A-6

Metro Baseline Re-Baseline: 04/20/10

external switching. The LAN shall also support RTU peer to peer

communications without the need for any external switching.

2. The RTU shall include one Ethernet communications interface integrated

directly into the PLC CPU for SCADA communications. It shall be possible

to configure a default routing gateway for the interface.

3. The RTU shall include a master/slave serial communications port

integrated directly into the PLC CPU for interface to

diagnostic/programming software and external communications gateways.

4. In-rack technology shall be used wherever possible to implement local

communications between the PLC and external subsystems that require

serial interfaces.

D Safety

1. The power-up initialization shall not unintentionally activate any control

output.

2. Sufficient error checking and sparse encoding shall be inherent in the

SCADA and remote I/O communications protocols such that it is

improbable for normal environmental noise to unintentionally activate

control output or incorrectly report the state of a discrete input.

3. Sufficient provisions shall be made in the RTU design and the design of its

components such that it is improbable for normal environmental noise to

unintentionally activate control output, incorrectly report the state of a

discrete input, or corrupt a logic calculation.

E Input/output SCADA Memory Mapping

1. A separate block of CPU memory shall be allocated for each of the

following inputs and outputs:

a. Internal diagnostics and registers

b. Analog inputs

c. Analog outputs

d. Discrete inputs

e. Discrete outputs

f. Remote I/O

g. Gateway I/O

h. Special calculations

2. Control memory shall be cleared on PLC startup or reset prior to the

enabling of any discrete output or serial protocol.

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American Audio VELOCITY - REV 4-05 Betriebsanleitung Seite 167