How exactly is it set up with N equal to two in the SIS configuration?
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In SIS logic, there are options such as 3 out of 2, 9 out of 2, 10 out of 2, etc. How exactly is it implemented to select N out of two in the configuration? Could you give a diagram? Is the circuit diagram used by each manufacturer to implement these 3-out-of-2, 9-out-of-2, and 10-out-of-2 functions the same? Additionally, it is required that during maintenance, 3 choose 2 should become 2 choose 1, 9 choose 2 should become 8 choose 2 or 6 choose 1, and 10 choose 2 should become 9 choose 2 or 6/7 choose 1. In that case, are the circuit designs for implementing the 3 choose 2, 9 choose 2, and 10 choose 2 functions identical? What exactly should it look like?
This post was last edited by Hariky on 2015-11-25 at 13:27. The change from 2oo3 to 1oo2 when maintaining a table is a problem with the exit mechanism. It is generally understood that an instrument in maintenance mode is in a faulty state. The function of the maintenance switch can be understood as forcing the instrument’s status to a fault state. The focus is on security; whereas 9 choose 2 becomes 8 choose 2 during maintenance, and it is not an exit mechanism. The function of the maintenance switch is to force the instrument’s status to a normal state. The focus is on usability. Also: I’ve never seen 9 choose 2 in my SIS logic design.
The method is simple: count the number of logical signals and compare it to 2; then use whether the count is greater than 2 as the logical output
This post was last edited by mainsj on 2015-12-4 22:55. 1. First, determine whether each signal is triggering an alarm (using functions such as greater than, less than, etc.), and include a bypass switch (to facilitate maintenance and implement an 8-to-1 logic). 2. Connect the N processed signals to the input pins of the first “NUMBITS” function block respectively, in order to count the number of alarms for those N signals. This functional block is available in TRICON. (NUMBITS is used to count the number of logical \"true\" values in a set of booleans); the names of function blocks from other manufacturers may vary slightly. 3. Connect N bypass switches to the input pins of the second “NUMBITS” function block in order to count the number of bypasses; the output of this function block is the number of bypasses. 4. If the “number of bypasses” is equal to (EQ) 0 and the “number of alarms” is greater than or equal to 2, then an alarm is generated (if there are no bypasses, N is set to 2). 5. An alarm is generated if the “number of bypasses” equals (EQ) 1 and (AND) the “number of alarms” is greater than or equal to 1 (N takes the value 1 when one signal is bypassed). The functional blocks of each system manufacturer vary slightly, and programmers have different approaches, but the functions can all be implemented. No need for a picture, right?
For this, I can provide you with the internal logic of HIMA’s N=2 packaging block