DESCRIPTION AND OPERATION
STATUS AND DATA BUFFERS
2 - 6
I-E96-315B
®
STATUS AND DATA BUFFERS
The status and data buffers hold status information and pro-
cess data traveling between the microcontroller and the slave
expander bus I/O. This allows the two asynchronous busses to
operate together and exchange information using handshake
signals.
MICROCONTROLLER
The HSS uses an eight bit microprocessor to control board
functions and communicate with the MFP through the slave
expander bus interface. The microcontroller controls the ana-
log-to-digital processing, passes position feedback and status
information to the MFP, reads control data from the MFP,
writes position demands to the digital-to-analog converter and
does self checks.
The microcontroller also controls the emergency manual cir-
cuit. This circuit provides isolated contacts the user connects
to +24 VDC, giving the operator a way to initiate control of the
hydraulic actuator in the event the MFP communications are
lost. By activating the raise or lower contacts the operator tells
the MCU to change the actuator position. The microcontroller
also writes to a digital output to tell the operator the module is
in the emergency manual mode of operation.
POSITION DEMAND AND OUTPUT
There are four parts to the position demand and output block,
the digital-to-analog converter, position error, servo amplifier
and dither oscillator. The output circuit provides proportional
plus integral plus derivative (PID) closed loop control on the
entire servo valve system. Figure
shows a simplified dia-
gram of the position demand and output circuit.
Figure 2-3. Position Demand and Output Circuit
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POSITION FEEDBACK
FROM DEMODULATOR
POSITION
DEMAND FROM
MICRO-
CONTROLLER
PROPORTIONAL
AMP
INTEGRAL AND
DERIVATIVE AMP
POSITION ERROR
MUX
DITHER
OSCILLATOR
SERVO AMP
SERVO
DRIVE
OUTPUTS
TP25046A
TRIP
BIAS
DAC
