Communication sequence
Process
Both the start and end of a data block are characterized by transmission pauses. The maximum period of time that may elapse between 2 successive characters is 3 times the period of time required for the transmission of one character.
The character transmission time (period of time required for the transmission of 1 char- acter) is dependent on the Baud rate and the type of data format.
Using a data format of 8 data bits, no parity bit and 1 stop bit, the character transmis- sion time is calculated as follows:
Character transmission time [ms] = 1000 * 9 bits / Baud rate
Data query by the master
Transmission time = n characters * 1000 * x bits / Baud rate
Identification of end of data query
3 characters * 1000 * x bits / Baud rate
Handling of data query by the slave ( 250 ms)
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| Reply by the slave |
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| Transmission time = n characters * 1000 * x bits / Baud rate | ||||
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| Identification of end of reply |
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| 3 characters * 1000 * x bits / Baud rate |
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Example | Identification of the data query or end of the reply with a data format of 10 / 9 bits. | ||||
| Waiting time = 3 characters * 1000 * x bits / Baud rate |
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| Baud rate |
| Data format [bits] |
| Waiting time [ms] |
| 9.600 |
| 9 |
| 2.813 |
| 19.200 |
| 9 |
| 1.406 |
| 3/14 |
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Siemens Building Technologies | CC1A7865.1en |
HVAC Products | 31.10.2002 |
