Count the number of closed inputs in module 0.

The solution to this problem requires the use of operations that are included in the integrative set. This means it is necessary to write the program as a functional block and then call it from the OB1 for cyclic execution. It is not possible to write the program in ladder format.
We will store the number of closed inputs in MB80 and use W10 as a pointer for the input normally examined. The first part of the program in OB1 consists of initiating these two variables at 0. The next statement calls the block FB4 that contains the main part of the program.
As a result of the unconditional block call statement, the development continues from the first statement in FB4.
The first two statements of this block load the complement of the input with the pointer MW10 into RLC. The channel direction is in the high byte and the module direction in the low byte. As MW10 is at 0, the first step will load the complement of the status of E0.0.
The next statement is a conditional jump: If RLC = 1, that is, if the complement of E0.0 is equal to 1, the input is open and the program continues after the INC label. On the other hand, if the input is closed, this jump does not take place and the program continues with the next statement.
The next four statements increase the value of MB80, that is the number that represents the count of the number of inputs that have been found closed. This value is first loaded into ACCU1 and then increased by 1 unit. The result is then again transferred to MB80. The purpose behind these statements and the preceding ones is to increase the variable MB80 if the input is closed and not increase it if the input is open.
In both cases the program reaches the group of statements labelled as INC and which, like the first action, increase the high byte of MW10, that is MB10 and the byte that represents the number of the input channel in the controlled loading operation seen earlier (for didactic purposes we have used a different operation to increase the byte). The recently obtained value is then compared to 7. If the result is equal to or less than 7, then the input exists and we should check its status by returning to the TEST label as specified in the conditional jump statement. On the other hand, if the value is 8 then the channel does not exist and we have to exit the block after having examined the eight possible inputs, from E0.0 to E0.7.
The section of the program between the label TEST and the statement SPB = TEST is performed eight times before returning to the starting block OB1 through the final BE statement. Each time MW10 will count a different value: in a hexadecimal succession of 0000, 0100, 0200, 0300, 0400, 0500, 0600, 0700; and each time the group of statements B MW10 and UN E0.0 will load the RLC with the complement of a different input of the module from the first to the last. The part of the program that goes from L MB80 to T MB80 is only loaded if the input normally checked is closed. This means that the increase of MB80 only takes place under this condition and, as the initial value of this merker byte is equal to 0, when execution of the block has been completed it will count the number of closed inputs.

If we want to analyse the closed inputs in module 1, simply load 1 as the initial value for MW10. It is also possible to determine the total number of closed inputs for the two modules. All that is required is to call FB4 on two occasions, the first time by initialising MW10 to 0 and the second time by setting it to 1. On the other hand, for MB80, it is only necessary to initialise it to 0 at the beginning of the OB1. We will leave the writing of this program up to you.

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