Fresenius Medical Care 4008 E Technical Manual page 469

Stepper motor activation
IC 14 constitutes the stepper motor controller module (SMC). IC 14 allows both full-step and
eighth-step operation, reversal of the direction of rotation, as well as a controllable motor current
limitation.
The digital control inputs and control outputs of the stepper motor controller are TTL-compatible
and can be directly connected to the microcontroller or to the gate array.
The step frequency, the direction of rotation and the module release of the stepper motor
controller are applied to port 1.1 to port 1.3.
Selection of full-step or eighth-step operation respectively is made by port A.7 of the gate array.
Via port A.4, the phase current can be set to two different rated values.
Interface to the hemodialysis machine
A level of 12 V is applied to the signals emitted by the hemodialysis machine. The signals are
limited to a voltage of 5 V by the optocoupler.
A 12-V level is applied to the ALARM and PUMP output signals by means of a transistor and a
pull-up resistor.
A serial interface is provided for expansions.
The voltage level of these signals amounts to 5 V.
8-172
Fresenius Medical Care 4008 4/09.03 (TM)