SMAC
LAC-26 Technical Reference Manual
4/29/2013 8
1.4 Output Driver Interface
The LAC-26 onboard output drivers are PWM switching amplifiers capable of supplying 3 Amps
continuous and 6 Amps peak (for 200 mS minimum) at a switching frequency of approximately 19.531
KHz. These drivers are intended for driving DC brush type motors or actuators. Both drivers share the
main power supply input and the peak voltage output to the motor will be nearly that of what is supplied.
The output drivers include an over-temperature sensor. If this sensor determines that the
amplifier’s temperature is greater than 140° C, the amplifier will then be disabled and the Over-
Temperature bit will be set in that axis' status word.
For applications requiring capabilities above those of the onboard drivers, the ability to interface
to external drivers is provided. This consists a 12-bit D/A
±
10 VDC analog output signal for each axis. In
applications where external drivers are not required, the analog outputs can be used for other purposes
(e.g.,: oscilloscope monitoring of following error or output command).
1.5 Analog to Digital Conversion (A/D) Interface
The LAC-26 provides a 5 channel, 10 bit A/D conversion interface with a +10 VDC reference and
analog ground.
For reverse compatibility purposes the A/D interface is actually
ten channels but
the user is only given access to channels 0, 1 and 2 while channels 6 and 7 are used internally for
monitoring the output current of the onboard drivers. The other channels are unavailable and
should be ignored.
Whenever a Tell Analog "TA" or Get Analog "GA" command is issued, the specified A/D channel
is converted and the result is either reported or stored for access by the user. Also, whenever the servo
loop for an axis is executed, the "current monitoring" channel for that axis is converted and the result is
stored for later access.
1.6 Serial Interface
The LAC-26 communicates with a host computer or a "dumb" terminal via an RS-232 serial
interface. The baud rate is user selectable from 300 to 19,200 baud with
9600 baud being the
default.
Characters are fixed at 8 bits in length with 1 stop bit and no parity. Software XON / XOFF
handshaking is
provided. Hardware handshaking is not supported at this time.
2. Macro Interrupt System
The LAC-26 employs a "Macro Interrupt System" to provide additional versatility in programming
the LAC-26. This system comprises 32 interrupt sources with corresponding vectors. When an interrupt's
source is enabled for operation and then becomes active, the current macro being executed is saved to a
so called macro stack and execution of the macro specified by that interrupt's vector table entry begins.
This happens to be similar procedure to that which the Macro Call (MC) command follows.
