Index Register

Index register(R) indicates device indirectly using with device. Index register has 16 ranges for R0 ~ R15, each range could be inputted by -32768~32767.

1. The restrictions on using index register

   Index register could be only used about application Instructions. Basic Instructions couldn’t use with it.
   Also, device S(Step Relay), T(Timer), C(counter) couldn’t use index register.

2. Action of index register.

Using at the word device.

          The value of indicated index is working as word unit.

Example	Description
Open	The value of R0 is 3.When the state of M00 is ON, the value of D10 from MOV command is to be D(0+R0), not to be D0. So, the moved value to D10 is the value of D03 by using MOV command.

Using word commands from bit device.

          It works as word unit by catching rest of indicated value that is divided by 16.

Example	Description
Open	R0 value is 100. When the state of M00 is ON, the value of D10 from MOV command is to be M(00+60). The value is the quotient of 100 divided by 16 that is expressed by word unit. So, the moved value to D10 is the word value of M60 by using MOV command.

Using bit commands from bit device.

         The value of indicated index is working as bit unit.

Commands and operands for acting bit device.
The third operand of TEST, TESTP, DTEST, DTESTP
The third operand of DUTY
The first and second operand of BITMOVE, BITMOVP