to determine when a complete data signal is generated by the prom the address sequence counter 102 can be two counters 114 and 115 connected as shown in fig1 the decoder 103 is a simple gating circuit as shown in fig1 the axis step counters 104 and 105 are identical and each comprise a counter 111 a step oscillator 112 and a motor phase sequencer 113 as shown in fig1 the latter two elements generate the drive signals to the motor drivers the stepping motors and drivers may be commercially available units such as those sold by icon division of usm corporation of cambridge massachusetts the preparation of a digitized pattern code which reflects the axis coordinates of the location of each stitch relative to the mechanical field of movement of the workpiece is well known however in the prior art the relationship betwen the rotary step of the stepping motor and the movement of the workpiece was generally directly proportional however the linkage assembly consisting of links 23 and 24 and levers 25 and 26 do not transmit the rotary motion of stepping motors 36 and 37 in a linear manner therefore the digitized coordinate values must individually be mathematically modified to reflect the functioning of the non linear linkage assembly and compensate for the errors therein the prom 100 therefore must be coded according to the modified digitized coordinate value a brief example of the compensating calculation which may be performed on any general purpose computer is shown in fig1 these calculations are.