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4.1 GENERAL
CHAPTER4
THEORY
This chapter describes the functions performed by the LASO printer. It also provides an understanding of
the printer's basic operating principles for field service personnel. Block diagrams and other drawings sup-
port the text.
4.2 INTRODUCTION
The LASO is a complete self-contained computer output hardcopy terminal. It consists of two basic compo-
nents (exclusive of the enclosure), a control/logic board which contains the power supply, and the printer
mechanism. The LASO block diagram (Figure 4-1) shows these components and how they functionally tie
together.
The control/logic board manages the printing, paper advancing, and communication processes. All other
components and major options connect to it. The control/logic board includes the following functional
components:
•
A microprocessor to manage the overall terminal operation
•
2
X
8192 bytes of read only memory (ROM) containing a microprogram and standard set-up
parameters to operate the terminal with its specific features
•
2
X
2048 bytes of random access memory (RAM) for microprocessor temporary storage and
input/output data storage
•
An 1/0
buff er that provides an interface between the microprocessor and the electromechanical
components in the printer mechanism
•
An asynchronous serial receiver/transmitter (USART) for data exchange with the host
computer
•
An interval timer for control/logic system timing
The printer mechanism includes all of the mechanical and electromechanical components necessary for
impact printing and paper/forms control. This includes:
•
A 9-wire printhead
•
A carriage motor for horizontal printhead position
•
A
stepper motor for vertical paper movement
•
A paper-out sensor
•
A
platen, bail bar, and friction assembly
The power supply converts the ac power line into de voltages used by the printer. A de to de converter
transforms the regulated 5 volt de power source to
+
12 volts and -12 volts.
4-1
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Troubleshooting
