Logic Flow Diagram (Figure 1-2) - Centronics 101AL Technical Manual And User Manual

Figure 1-1. MODEL 101AL PRINTER (TOP COVER REMOVED)
1.2 LOGIC FLOW DIAGRAM (Figure 1-2)
If the input device transmits serial data (100-9600 Baud) then an optional RS232 interface is re-
quired to assemble the serial data, then transfer it in parallel to the input buffer in the printer.
Paper movement is initiated by a line feed, vertical tab and form feed function. The Vertical Format
Unit (VFU) tape reader provides vertical tab and top of form spaeing control by means of a perforated
paper tape. I n addition, the printer recognizes the following special control codes: bell,delete, select, de-
select and elongated character, as described in Section 1.3.3.
Once a line of printable characters is stored in the buffer, head motion is initiated by activating the
forward clutch, causing the print head to move from left to right across the paper. With the head in motion,
data is transmitted from the buffer to the character generator. From there, character write pulses are sent
to the driver circuits, which energize the print head solenoids causing the print wires to form the characters
on the paper.
Rev. E
DATA
INPUT
- -
TIMING
VFU
OPERATOR
TAPE
BUZZER
FENCE
READER
PANEL
• •
t
,
CONTROL
HEAD MOTlON_
CLUTCH/
CONTROL -
1. PRINT COMMAND
(CR OR LAST CHAR.)
PAPER MOTION_
PAPER
2. PAPER MOVEMENT
~
MOVEMENl"
(LF, VT, FF)
CONTROL
SOLENOID
3.
SPECIAL FUNCTIONS
(BEL~DELET~EX~
TIMING
CHAR)
1
SHIFT
- ' CHJlIRACTER
I
WRITE
_J
PRINT
1
-
REGISTER
-
I
GENERATOR
J
PULSES"
I
HEAD
BUFFER
Figure 1-2. 101AL PRINTER LOGIC FLOW DIAGRAM
1-2