Epson LX-HOO Technical Manual page 53

array detects the trailing edge of the STRB signal, it automatically sets the BUSY signal HIGH and
latches the transferred data.
in the input buffer. The CPU analyzes each byte of data to determine whether it is a control code
or print data, then returns the ACK signal to the interface.
the BUSY signal is set HIGH.
of data. If the data is not a printing command (CR), the CPU sets the printing mode and parameters
and transfers the data to the line buffer. The line buffer is shown in Figure 2-16.
The line buffer temporarily stores the data for one line using the format shown in Figure 2-16, and
also contains the command flags (1 6 bits), for attributes 1 and 2, for each character. The command
flags indicate what kind of command or mode is specified for the character. According to the
command flags, any of the EPSON ESC/P commands, NLQ, underline, emphasized character, and
font selection, is specified for the character.
When either the CPU detects a printing command (CR) or the line buffer becomes full, the printing
process (interrupt routine) is started.
The CPU transfers the character codes from the line buffer to the CG (Character Generator), and
transfers image data to the CG copy area. The CG copy area refers to the attribute flags in the line
buffer and expands the image data. The expanded data is then transferred to the image buffer.
The CPU writes the (vertical) dot patterns in the image buffer to port HD of the gate array (writes
and outputs the FIRE signal (which corresponds to the dot patterns expanded in the image buffer)
to the gate array.
When the NLQ mode is selected, note the following difference from the Draft mode:
During command analysis in step @, if the data is determined to bean NLQ character, the steps after
step @ are repeated two times for every one pass (NLQ requires two-pass printing).
When the download mode is selected, the following point is different from the draft mode:
When referencing the CG in step @, the CPU accesses the down load buffer but not the CG.
Attribute
Character
1
code
Fig. 2-16. Line Buffer
Attribute
Character
2 code
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2-21
REV.-A