It's generalized to use a full 16 bits, but could be shortened or expanded to suit the application. The MSB is taken directly, and the algorithm for subsequent bits is the same for the remaining bits regardless of the number. G15 to G00 are gray code inputs from an encoder or other such device. Subsequent G bits are XOR'd with the previous B bit. Circuit valid for mechanical starters, solid state starter, and vari-frequency drives.
Circuit includes a momentary start pulse and an auxiliary contact sealin delay timer.
Circuit also provides a motor jog function. Jog switch must be a physical, wired, non-maintained switch for safe operation. These OPs include the OP20, OP5, OP15, OP7, or OP17. These OPs include the OP7, and OP17. This version of the subroutine is for a Siemens S7-22x and was translated from an older S5 function block which has been used in numerous applications.