Misc In; Stepper Motor Control - GE Medical Systems PRODIGY Service Manual

2.5.18 MISC IN

Bit Name
0 BOOT JUMPER
1 CPU_P1_2
2 Unused
3 Unused
4 Unused
5 Unused
6 Unused
7 Unused

2.5.19 Stepper Motor Control

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2-58 System Overview
The misc. output register is used to control the misc input functions listed in
the following table
R/ Def. Description
W
R N/A JP4, placed to force firmware to remain in boot code.
R N/A Input from CPU port 1, pin 2 (diagnostic use only).
N/A N/A Expansion room.
N/A N/A Expansion room.
N/A N/A Expansion room.
N/A N/A Expansion room.
N/A N/A Expansion room.
N/A N/A Expansion room.
The stepper motors use the same interface design as used on IQ and Prodigy.
The FET exhibits a lower voltage drop and hence provides more available
power at the drives for a given source voltage - essentially recovering the
voltage lost in dropping the DC supply from the 26V used on IQ/Prodigy to the
24V which is readily available in commercial switchers. Diodes are placed in
series on the Centent power lines to prevent back EMF generated when the
arm is moved manually from reaching the 24V planes and damaging the
cSBC. A dual FET circuit is used to minimize the voltage drop on the 24V
plane due to in-rush current when the motors are enabled. A circuit in the
FLEX implements a 2 stage turn on when the firmware lowers /motor_enable.
Q15 is enabled first to provide 24V to the Centents through R381 and R384,
thus limiting the in-rush current. After the current pulse has stabilized Q14 is
enabled to bypass the inrush limiting resistors. Q15 is then disabled and the
motors are at full power. An PTC is provided on the source of Q15 such that
the current limiting resistors will not be smoked if Q15 is inadvertently left
enabled.
PRODIGY Service Manual (Rev C - 2000)