Service manual

PN 4237242C
2.4-7
INSTRUMENT DESCRIPTION
SYSTEM CONTROL
2
Commands to the GAL are provided by an 8-bit latch. Seven bits of this latch represent the
parameters SENSOR MODE, STOP, ENABLE, SENSOR ENABLE, DIRECTION, STEP and
POWER. The eighth bit does not go to the GAL. It is passed through a buffer to the circuit
connector and is used to control one solenoid. The output of the latch is also attached to a
unidirectional bus buffer. By enabling this buffer, the host CPU can read the command latch.
A motor sensor buffer is also provided by each Motor Controller circuit. This is an 8-bit buffer
that can be read by the CPU. Six bits can be used for sensors and two bits are assigned for
interrupts. Each GAL is assigned one of the sensors, should it require sensor information to
control a motor.
Solenoid Controller
The solenoid controller is a third Motor Controller circuit adapted to handle only solenoids.
The latch bits for STOP, ENABLE, DIRECTION, and STEP modes are now used to represent
four solenoids. The GAL is programmed to pass these ENABLE signals through to the four
lines used for the stepper motor phases. Since each control circuit of a motor controller
already handled one solenoid, the entire solenoid controller can control 10 solenoids.
Support Circuitry
The support circuitry for the DRA card consists of Power Supply Conditioning, a Bus
Interface, an Internal Bus Controller, and the Oscillator circuit. The DRA card uses +5 V from
the motherboard bus connector. This supply is fitted with a spike supressor and a large filter
capacitor when it enters the card. A bypass capacitor is also provided for the input line of
each IC.
The Bus Interface circuitry allows the DRA card to communicate with the AT motherboard
and abides by the AT convention. There is a bidirectional data bus buffer, address buffer, and a
command and interrupt buffer.
The DRA card has its own internal data bus for the onboard logic devices. An Internal Bus
Controller is responsible for the operation of this local bus.
The AT bus provides an 8-MHz clock signal, but the DRA card has its own 1-MHz Oscillator
circuit. This 1-MHz Oscillator circuit is used exclusively by the four, 8254 motor control
timers.
Inputs
P1, P2 - AT bus connector
Outputs
Table 2.4-3 DRA Card Output Connectors
Connector Connected To
J1 Motor/Solenoid Driver card
J2 Motor/Solenoid Driver card
J3 Motor/Solenoid Driver card
P1, P2 AT bus connector