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. Data from the host computer are then read into the input
buffer as ASCII data. (Printers with CT or CTHI options for
twinax/coax/IPDS operation convert IBM EBCDIC code to ASCII before
processing the 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 2–8.)
During self–tests, data stored in ROM are used to build the dot image buffer.
Operation then proceeds as in normal printing.
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