Specifications

2–8
Principles of Operation
Normal Operation
In normal operation, the user presses a switch on the control panel to put the
printer on–line. Host computer data are then read into the input buffer as
ASCII data. The data in the input buffer are compared to tables stored in
memory to determine the matrix and location of each character The
characters are then built in the dot image buffer.
Information from the dot image buffer is synchronized with printer
requirements using the magnetic pickup signal, then shifted to the hammer
drivers. The selected hammers are fired.
When all dots in a row are printed, the paper advances one dot row and the
next dot row of data from the dot image buffer are synchronized then shifted
to the hammer drivers. Vertical paper movement is delayed to allow double
printing if adjacent dot printing is required. (See Figure 2–7.)
During self–tests, data stored in ROM are used to build the dot image buffer.
Operation then proceeds as in normal printing.
Control Panel
Printer Setup
Printer Enable
Input Data Buffer
(Dynamic RAM)
ASCII data (DPU)
**
** Controlled by
software, executed
by hardware.
Printer Interface:
Host Input Data
Build dot image from
lookup tables. Put into
Dynamic RAM (DPU).
Synchronize timing to
codewheel (MPU)
software.
Demand hammer load
data be shifted to
hammer driver. **
Fire hammers on next
MPU. (Software timers.)
All dots in
row
printed?
Move paper.
(Mech. Driver)
YesNo
Software
decision
Figure 2–7. The Print Cycle