DMP 200  (260-1254)              Buffer                Faxback Doc. # 4430

The DMP-200's ability to temporarily store data is one of its main advantages
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 (that is, LF or CR), the buffer is
emptied and all data is printed on the paper. What happens after the buffer
data prints depends on the circumstances. In some cases, printing continues on
the same line; in others, the print head moves to a different position
relative to the paper.

In the DP mode, commands for changing fonts, line feed, and so on, can be
stored in the print buffer until data is printed.

TIPS ON THE PRINTER BUFFER

FOR DP, WP, AND GRAPHICS MODES:

* The buffer allocates a fixed number of dots, depending on the character
  width selected. The buffer empties when the stored data equals that 
  number.  Printing resumes at the start of the next line.

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

* The form-feed code (FF=12 decimal) automatically activates printing (if 
  the code is received by the printer). the buffer prints and thee print 
  head moves to the next top-of-form line without a carriage return

* The carriage-return code (CR=13 decimal) automatically activates printing
  (assuming that at least one character code is already in the buffer). If 
  you select carriage return only (via hardware), the printing position 
  moves to the start of the current line, and the next buffer full prints 
  subsequent characters over the current line. Otherwise, subsequent 
  characters print at the start of the next line.

* The line-feed code (LF=10) automatically activates printing. The buffer
  prints and the print head moves to the next print line without a carriage
  return.

* If the computer delays more than a second before sending the next print
  code, the buffer prints. Printing continues from the current position.

* The head positioning sequence 27 16 n1 n2 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 on the 
  current line at the dot address specified by the command.

* If you select a character set of different dot density, the data in the
  buffer prints. Codes for changing character sets are: 27 17, 27 18, 27 19,
  27 20, 27 23. Printing continues in the current line with the new char-
  acter style.

* Dot graphics printing continues from the current character position.

* When a start Bold or end Bold is received, the buffer is printed.

* Bold printing continues from the current character position.

GRAPHICS MODE ONLY:

* When the end Graphic Mode is received, the Printer returns to the prev-
  ious print mode and printing continues in the same line from the current 
  print position.

NOTES:
  In the description, "next line" means the new line reached by performing
  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.

  Repeat data can cause a buffer full or overflow condition as well as 
  single characters.

(abo-07/26/93)