Index Registers

The index registers are battery backed if the panel has battery backed memory. The index registers are cleared to zero when the panel application is updated.

You can use the index registers to specify the indirect address. With the support of indirect addressing, an object or macro can be designed to access different sets of data at run time.

Examples

1. The word address W[$I30] is equivalent to W2000 when the value of $I30 is 2000.
2. The word address $U[$I0+123] is equivalent to $U223 when the value of $I0 is 100.
3. The bit address $U[$I2].a is equivalent to $U0.a when the value of $I2 is 0.
4. The word address [$I2]:W100 is equivalent to 3:W100 when the value of $I2 is 3.
5. The bit address [$I0]: W[$I1+10].f is equivalent to 5:W20.f when the values of $I0 and $I1 are 5 and 10 respectively.
6. The driver of SIMATIC S7 (Ethernet) allows index addressing for data blocks. For examples, the addresses shown below are valid now.

   DB[$I3].DBW100

   DB[$I5+2].DBD[$I10+16]

   DB[$I0+2].DBX[$I1].5

   Note: The support of data block indexing can be provided for any PLC driver upon request.

Notes:

1. It is your responsibility to make sure that values in the index registers will result in valid addresses at runtime. The software has no way of checking the validity of the use of index registers.
2. The offset values must be a positive number, and the maximum offset value is 65535. And the offset value can be a hexadecimal number if the number is followed by letter h or H.
3. Only $I0~$I15 can be used for the node address (PLC address), and no offset value is allowed.
4. Make sure the PLC driver you are using supports indirect addressing.