ABB AC 31 Technical Manual page 163

Program Optimization
The frequency and number of pulses may be modified during the execution of the NPULSE
function.
With each change of the validation input status 0 -> 1, the pulse generation restarts for the
predefined pulse number.
A second output commanding an external relay, which enables the commutation of the
direction, should be used when a motor requires a second pulse generator for half duplex
operation.
The output of the step motor command is available on all of the 40 and 50 series central units
transistor or relay output versions.
In the case of relay outputs you must ensure that the maximum frequency of relay
commutation, which is a resistive load of 100 Hz, is not exceeded,.
The motor command is ensured whatever the other functions are that are used by the central
unit, for example the interruptions.
Page 6-10
ABB Control - AC 31
1SBC 260400 R1001-b 06.99