DMP-442  (260-2822)             Buffer                 Faxback Doc. # 4362

The printer's ability to temporarily store data is one of its main advant-
ages over a typewriter. Codes sent to a typewriter (that is, keys you press)
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 emp-
tied and all data is printed on the paper. What happens after the buffer 
data is printed depends on the circumstances. In some cases, printing con-
tinues 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 print 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 print 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).
If you select LF only in the menu, the buffer prints and the print head 
moves to the next top-of-form line, without a carriage return. Otherwise,
the printing position is set at the start of the next top-of-form line.
* The carriage return code (CR = 13 decimal) automatically activates print-
  ing (assuming at least one character code is already in the buffer). If
  you select CR only in the menu, the printing position moves to the start
  of the current line, and the next buffer full prints the subsequent 
  characters over the current line. Otherwise, the printing position is 
  set at the start of the next print line.
* The line feed code (LF = 10) automatically activates printing. If you 
  select LF only on a menu, the buffer prints and the print head moves to 
  the next print line, without a carriage return. Otherwise, the printing 
  position is set at the start of the next print line.
* If the computer  delays more than 0.5 seconds before sending the next 
  print code, the buffer prints. Printing continues from the current 
  position.
* The dot positioning sequence 27 16 n1 n2 prints the buffer if the desig-
  nated position is to the left of the current position. 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 cur-
  rent 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, 27 29, 27 47. Printing continues in the current line 
  with the new character style.
* When the printer receives the start graphics mode (18) followed by stand-
  ard or condensed characters, the buffer prints. Dot graphics printing 
  continues from the current character position.

GRAPHICS MODE ONLY:
* When the printer receives the end graphics command and returns to a stand-
  ard or condensed character printing condition, the buffer prints. The 
  printer returns to the previous 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 causes the paper to move 
  in the reverse direction.
* Repeat data can cause a buffer full or overflow condition. the printer
  ignores the overflow characters and does not print them.

(css 07/27/93)