DMP 130A  (260-1280A)      Buffer Operation            Faxback Doc. # 4313

The DMP-130's ability to temporarily store data is one of its main advant-
ages over a typewriter. Codes sent to a typewriter (i.e., keys pressed) 
are transferred immediately to the paper. Codes sent to a Printer are not 
printed immediately; they are stored in a separate section of memory in the
Printer called the buffer. When the buffer fills, or certain codes are 
received (e.g.,LF or CR), the buffer is emptied and all data is then printed
on the paper.  What happens after the buffer data is printed depends on the 
circumstances. In some cases, printing continues on the same line; in others,
the print head is moved to a different position relative to the paper.

In the DP mode, commands for changing print fonts, line feed, etc., can be
stored in the buffer to take effect when the data is dumped to paper.

Understanding how the buffer works is important if you wish to gain full
control of the DMP-130.

HINTS AND TIPS ON THE DMP-130 BUFFER

DP, WP, AND GRAPHICS MODES

* The buffer allocates a fixed number of dots, depending on the character
  width selected. The buffer is emptied when the data stored equals that
  number. Printing resumes at the start of the next line unless DIP switch
  1-2 is set to ON (CR only). If different character widths have been used 
  on the same line, the last character added may exceed the dot count. The
  buffer is printed without this last character.

* The last character received by the buffer is printed at the beginning of
  the next print line following an automatic line feed and carriage return.

* The form feed code (FF = 12 decimal) automatically activates printing (if
  the code makes it to the Printer). If LF only has been selected (DIP 
  switch 1-3), then the buffer is printed and the print head moves to the 
  next top-of-form line without a carriage return to the beginning of the 
  line. Otherwise, the print head is positioned at the beginning of the 
  next top-of-form line.

* The carriage return code (CR = 13 decimal) automatically activates print-
  ing (assuming at least 1 character code is already in the buffer). If 
  carriage return only has been selected by the setting of DIP switch 1-2, 
  the print head is moved to the beginning of the current line and the next
  buffer-full condition will result in printing over the current line. 
  Otherwise, subsequent characters will be printed at the start of the next
  print line.

* The line feed code (LF = 10 decimal) automatically activates printing. 
  If LF only has been selected (DIP switch 1-3), then the buffer is printed
  and the print head moves to the next print line without a carriage return 
  to the beginning of the line. Otherwise, the print head is positioned at 
  the start of the next print line.

* If the computer delays more than a second before sending the next printer
  code through the parallel interface, the buffer is printed. Printing
  continues from the current position.

* The head positioning sequence (27 16 n1 n1) prints the buffer. Printing
  continues in the current line at the dot address specified by the (27 16)
  command.

DATA AND WORD PROCESSING MODES ONLY

* The backspace command activates printing. Printing continues in the 
  current line at the dot address specified by the command.

* If a character set of different dot density is selected, the data in the
  buffer is printed. Codes for changing character sets are: (27 17), 
  m(27 18), (27 19), (27 20), (27 23), (27 29), (27 31), and (27 32). 
  Printing continues in the current line with the new character style.

* Dot graphics printing continues from the current character position.

* When a start super-/subscript, italics, microfont, compressed
  correspondence, proportional quality 12 CPI, or compressed code is 
  received, the buffer is printed.

GRAPHICS MODE ONLY

When the end graphics mode command is received, the Printer returns to the
previous print mode and printing continues in the same line from the 
current print position.

NOTE 1: In the description, next line means the new line performed by a 
line feed operation. In data processing mode, if a reverse line feed has 
been set in the memory, the line feed operation will cause paper to move
in the reverse direction.

NOTE 2: Repeat data can cause a buffer full condition, as well as an
overflow by single characters.

(css 07/26/93)

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