Many Modbus indications (one bit data) in the device are coded as MOM and MCD bit pairs. The client detects a fast indication 0￫1￫0 change, if the two bits are combined with logical OR operation. The SPA protocol automatically includes this combination of MOM and MCD bits.
Reading of 16 bit registers
As an example, register 223 contains 8 MOM + MCD bit pairs in 16 separate bits. The register can be read as a regular 16 bit register revealing every bit.
Example:
>25R223I1/16:CC <25D:1/0/0/1/1/1/1/0/0/0/1/1/0/0/1/1:CC(I21/28) It is also possible to read the logical OR operation result of every bit pair. Since there are 8 pairs, the OR results are 8 bits:
>25R223I21/I28:CC <25D:1/1/1/1/0/1/0/1:CC(I51) Reading is also possible to perform in unsigned decimal form:
>25R223I51:CC <25D:175:CC(I52) Or in hexadecimal form:
>25R223I52:CC <25D:AF:CCReading of 32 bit registers
If the two consecutive 16 bit registers (32 bits) contain all 16 MOM + MCD bit pairs, then the logical OR operation result (=16 bits) can be read out in one query. Assuming the registers are 223 and 224.
(I61) In unsigned decimal form:
>25R223I61:CC <25D:43567:CC(I62) In hexadecimal form:
>25R223I62:CC <25D:AA2F:CC