AS‐i Master Operating Phases
(Original Document)
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Illustration of the Architecture
The diagram below shows the flowchart for the different operating phases.
Description of Constituent Elements
The table below shows the different actions included in the each of the operating phases.
Step
Phase
Description
Initialization
Initialization
The master is initialized at each power up or during operation when it switches from Configuration mode to Protected mode. During this initialization, which lasts approximately 1 second, the AS-i bus input and output images are set to 0, from the PLC application.
Start-up
Detection
The AS-i master scans the AS-i bus to detect the number of slaves present, the addresses used, and the identification of each device. The slaves detected are recorded in the LDS (list of detected slaves) and the Identification Codes are recorded in the AS‐i bus Configuration/Identification table. If no slave is detected on the AS‐i bus, the AS-i master remains in this phase and waits for a device to be present before switching to the activation phase.
Activation of slaves in configuration mode
All slaves detected on the AS‐i bus are activated. Specifically, this mode allows the current AS‐i bus configuration to be saved in the reference configuration (simplified method for programming the desired configuration).
Activation of slaves in protected mode
The only slaves activated are those whose identification conforms to the one included in the reference configuration.
The active slaves are recorded in the LAS (list of active slaves).
Nominal operation
Data exchange
The master sends the data (output data) cyclically to the different slaves, and in exchange receives acknowledgement messages (input data). If there is a transmission error, the master repeats the call in question. The cycle time for polling all the slaves on an AS-i line is less than 5 ms.
Management
It is during this phase that:
  • Modification of the slave parameters occurs,
  • The auto-addressing function is executed,
  • The AS-i bus configuration is saved in the reference configuration,
  • All instructions except for cyclic data exchanges are sent.
Recording
The LDS and LAS lists are managed during this phase when there is a connection or disappearance of a device on the AS-i bus. A slave that has just been recorded in the LDS (list of detected slaves) is activated, then recorded in the LAS list (list of active slaves) depending on the operating mode of the AS‐i master. A faulty slave disappears from the LDS and the LAS and triggers a configuration fault.