Page 4-2
GSA 8X/GSM 85(A) Installation Manual
Revision R
190-00303-72
The GSA 8X accepts power from 28-volt aircraft electrical systems. Aircraft power is supplied to the
GSA 8X through two power-input pins labeled AIRCRAFT POWER and AP DISCONNECT.
AIRCRAFT POWER (Pin N) supplies power to the GSA 8X micro-controller, and associated circuitry,
whereas AP DISCONNECT (Pin P) supplies power to the drive motor and the engagement solenoid.
Aircraft power is routed to the AP DISCONNECT pin through the normally closed AP DISC switch in
the aircraft. Whenever the AP DISC switch is depressed, power to the motor-drive and solenoid-drive
circuits is interrupted, thereby guaranteeing removal of motor and solenoid current.
4.3
RS-485 Serial Data
The GSA 8X communicates with the GIA 63/GIA 63W over two RS-485 serial ports. Two unique
protocols are used, one for startup and bench testing, and the other for normal operations.
Table 4-3. RS-485 Pins
Pin Pin
Name
I/O
J
RS-485 1 A
I/O
T
RS-485 1 B
I/O
S
RS-485 2 A
I/O
E
RS-485 2 B
I/O
4.4
Servo Program Inputs
The servo program inputs (listed in Table 4-4) are installation straps that program the GSA 8X servo
actuator to function in the appropriate flight-control axis, as defined by Table 4-5. The avionics installer
grounds the appropriate program line(s) of the GSA 8X to the program ground pin(s), per Table 4-5 to
force the desired servo functionality. The GSA 8X read the states of these lines once, at power-up to
determine the required servo functionality.
Table 4-4. Servo Program Inputs
Pin Pin
Name
I/O
H
SERVO PROGRAM 1
In
G
SERVO PROGRAM 2
In
F
SERVO PROGRAM 3
In
Table 4-5. Servo Function Logic Table
Servo Program Pins
Pin F
SERVO
PROGRAM 3
Pin G
SERVO
PROGRAM 2
Pin H
SERVO
PROGRAM 1
Servo Function
Open Open Open
Bench-Test
Open Open Ground Pitch
Primary
Open Ground Open
Roll
Primary
Open Ground Ground Yaw
Primary
Ground Open Open
Pitch
Trim
Ground Open Ground
Roll
Trim
Ground Ground Open
Yaw
Trim
Ground Ground Ground
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