DMP 440  (260-2808)               Buffer               Faxback Doc. # 4451

Buffer size- Approximately 6K

The DMP-440'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 buf-
fer 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 buf-
fer data prints 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 fonts, line feed, and so on, can be 
stored in the printer buffer until data is printed.

TIPS ON THE DMP 440 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 data stored 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 DMP 440).

If you select "LF only" (DIP switch 1-3), the buffer prints and the print 
head moves to the next top-of-form line without a carriage return. Other-
wise, the printing position is set at the start of the next top-of-form 
line.

* 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" (DIP switch 1-2), the 
  printing position moves to the start of the current line, and the next
  buffer full prints subsequent characters over the current line. Other-
  wise, subsequent characters print at the start of the next line.

* The line feed code (LF = 10) automatically activates printing. If you 
  select "LF only" (DIP switch 1-3), 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 a second 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  
  designated 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 in 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 31, 27 32. Printing continues in the current
  line with the new character style.

* When the printer receives the start graphics mode (18) followed by stand-
  ard characters, the buffer prints. Dot graphics printing continues form 
  the current character position.

GRAPHICS MODE ONLY:

* When the printer receives the end graphics code and returns to a stand-
  ard or condensed character printing condition, the buffer prints. The 
  DMP-440 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 perform-
  ing a line feed operation. In data processing mode, if a reverse line 
  feed is set in the memory, the line feed operation causes paper to move 
  in the reverse direction.

* Repeat data can cause a buffer full or overflow condition. The overflow 
  characters are wrapped around and printed at the beginning of the next 
  line.

(abo-07/26/93)