Difference between revisions of "BACnet MS/TP"
From BACnet Wiki
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| Data CRC LSByte || if len non-zero | | Data CRC LSByte || if len non-zero | ||
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| + | Prior to Revision ** (prior to 135-2006) Max APDU was 480 bytes. | ||
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| + | NPCImax = 9 + 6 byte MAC + 7 byte MAC = 22 | ||
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| + | So [[NSDU]]max = 480 + 22 = 502 | ||
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| + | And NSDUmax + 10 (above) = 512 | ||
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{{Keyword List}} | {{Keyword List}} | ||
Revision as of 23:21, 11 November 2018
BACnet "Master-Slave/Token-Passing" is the optional, RS-485 based physical layer for BACnet. It is based on cheap, relatively slow, serial communications.
Starting with Addendum 135-2008ab, 9600 and 38400 are the required baud rates and all of the others (19200, 57600, 76800, and 115200) are optional
| 0x55 | Framing 1 |
| 0xFF | Framing 2 |
| Frame Type | |
| Dest MAC | |
| Src MAC | |
| Len MSByte | |
| Len LSByte | |
| Header CRC | |
| Data | if len non-zero |
| Data CRC MSByte | if len non-zero |
| Data CRC LSByte | if len non-zero |
Prior to Revision ** (prior to 135-2006) Max APDU was 480 bytes.
NPCImax = 9 + 6 byte MAC + 7 byte MAC = 22
So NSDUmax = 480 + 22 = 502
And NSDUmax + 10 (above) = 512
| APDU BBMD BVLC BVLL DADR DNET Encoding I-Am LSAP MAC NPCI NPDU NSAP NSDU SA SADR SNET |
| Edit this box. |
