Centronics 101AL Technical Manual page 25

SECTION 4
THEORY OF OPERATION
4.1 INTRODUCTION
This section on the theory of operation contains a detailed de-
scription of each major function performed by the Model 101AL printer
electronics. Figure 4-1 shows a basic functional diagram of the printer
electronics.
Throughout this section, reference is made to the schematic dia-
grams contained in Section 7. The section is organized as follows:
Paragraph 4.2 Basic Timing
4.3. Initializing the Printer (Prime, Select)
4.4 Data Input (Data, Strobe, Busy, Acknowledge)
4.5 Shift Register (Buffer)
4.6 Character Printing
4.7 Paper Movement (Line Feed, Vertical Tab, Form Feed)
4.8 Special Functions (Bell, Paper Empty, Delete,
Motor Control)
4.9 Power Supplies
.10 Outputs from LSI chips
4.2 BASIC TIMING
The basic timing clock for the printer electronics is derived from
signal OSC. This OSC signal is generated on LSI chip ME9 pin 25. The fre-
quency of OSC, determined by the RC circuit (R41-C9) on pin 26 of this chip,
ranges from 100 to 200 KHz.
4-1