ArchitectureProperty Management System - Communication Interface
Asynchronous Transmission
Line Control | The characteristics of the signals transmitted across the communications link are as | |||
Characteristics | follows: |
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| Table | |
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| Item |
| Conditions | |
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| Control Method |
| Contention method (point to point) | |
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| Operating Mode |
| Half duplex (if modems are used, set to full duplex) | |
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| Synchronization |
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| Data Rate |
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| 1200, 2400 or 4800 bits/second (bps) |
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| Frame Contents |
| ASCII (7bits) | |
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| Error Control Method |
| VRC: Parity, LRC: BCC | |
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| Bit Transmission Order |
| Priority is given to low order bits. | |
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| Transmission Intervals |
| At each data generation. When a stream of information is | |
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| transmitted to the NEAX continuously, an interval of 0.5 |
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| seconds or more should be given between messages. Each |
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| message must be delimited by the EOT code. |
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| Priority Sequence |
| Primary office: NEAX | |
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| Secondary Office: PMS |
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| Stop bit |
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| 1 bit or 2 bits |
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| Error Control |
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| VRC: Even, odd or no parity. |
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| LRC: (BCC) Exclusive OR of the message text, starting after the |
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| STX, and ending with (and including) the ETX. |
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| Message Composition |
| One message constitutes one record; SOH, TTB and ETB are not | |
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| used. |
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| Message Length |
| Variable length, maximum of 128 characters (including STX and | |
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| ETX). |
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| Electrical Interface |
| EIA | |
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| Signal Form |
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| EIA |
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| Interface Distance |
| Maximum of 50 feet between the NEAX and the PMS when not | |
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| using a modem. |
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| Word Framing |
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| 10 bits (1 start, 7 data, 1 parity, 1 stop) or 11 bits (1 start, 7 data, |
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| 1 parity, 2 stop) |
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Page 4 |
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