Shift and Rotate Instructions

Overview of Shift Instructions

You can use the Shift instructions to move the contents of input IN bit by bit to the left or the right (see also CPU Registers). Shifting n bits to the left multiplies the contents of input IN by 2 to the power n (2 n); shifting n bits to the right divides the contents of input IN by 2 to the power n (2 n). For example, if you shift the binary equivalent of the decimal value 3 to the left by 3 bits, you obtain the binary equivalent of the decimal value 24. If you shift the binary equivalent of the decimal value 16 to the right by 2 bits, you obtain the binary equivalent of the decimal

value 4.

The number that you supply for input parameter N indicates the number of bits by which the value is shifted. The bit places that are vacated by the Shift instruction are either padded with zeros or with the signal state of the sign bit (0 stands for positive and 1 stands for negative). The signal state of the bit that is shifted last is loaded into the CC 1 bit of the status word, see also CPU Registers. The CC 0 and OV bits of the status word are reset to 0. You can use jump instructions to evaluate the CC 1 bit.

The following Shift instructions are available:

·       SHR_I :       Shift Right Integer

·       SHR_DI :    Shift Right Double Integer

·       SHL_W :     Shift Left Word

·       SHR_W :    Shift Right Word

·       SHL_DW :  Shift Left Double Word

·       SHR_DW : Shift Right Double Word