DMP 2120  (260-2811)            Buffer                  Faxback Doc. # 4610

The DMP-2120's ability to temporarily store data is one of its main advant-
ages over 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 call the buffer. When the buffer
fills, or certain codes are received (i.e., LF or CR), the buffer is emptied
and all data is 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 affect when the data is dumped to paper.

HINTS AND TIPS ON THE DMP-2120 BUFFER....

* 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.

  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 makes it to the Printer). If LF only has been selected  
  (LF-CODE:setting), then the buffer is printed and the print head moves to  
  the next Top-of-Form line without a carriage return to the start of the  
  line. Otherwise, the printing position is set at the start of the next   
  Top-of-Form line.

* The Carriage Return (CR = 13 decimal) automatically activates printing
  (assuming at least one character code is already in the buffer). If Carri-
  age Return only has been selected (CR-CODE:setting), the printing position
  is moved the start of the current line, but the next buffer full will 
  print subsequent characters to the start of the next line regardless of 
  the CR-CODE setting. Otherwise, subsequent characters will be printed at 
  the start of the next line.

* The Line Feed (LF = 10) automatically activates printing. If LF only has
  been selected (LF-CODE:setting), then the buffer is printed and the Print  
  Head moves to the next print line without a carriage return to the start 
  of the line. Otherwise, the printing position is set at the start of the 
  next print line.

* If the computer delays more than 0.5 second before sending the next print
  code, the buffer is printed. Printing continues from the current position.

* The Dot Positioning sequence (27 16 n1 n2) prints the buffer, if the
  designated position is at the left from 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 a character set of different dot density is selected, the data in the
  buffer is printed. Codes for changing character sets are: 27 17, 27 18, 27
  19, 27 20, 27 23, 27 29. Printing continues in the current line with the 
  new character style.

* When the start Graphics Mode (18) is received followed by  the Standard 
  or Condensed characters, the buffer is printed.

GRAPHICS MODE ONLY:

* When the end Graphics is received and returns to a Standard of Condensed
  character printing condition, the buffer is printed.

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 
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 or overflow condition, but the
overflow characters are ignored and not printed at the start of the next 
line.

The optimizer function allows the following: If the printer receives a 
spacing code (fixed space and/or proportional space), the carriage moves 
only the shortest distance, and the action takes place without unnecessary 
movement. This saves printing time.

This function is canceled, and uni-directional printing is performed if the 
PRT DIR setting is set to UNI DIR on the control panel. This increases 
printing time but offers better fine vertical alignment. When the character 
data (SP, proportional space, or printable code) is sent to the printer 
within a 0.5 second interval, the printer automatically stores it until (1)
function codes are sent, or (2) the interval is more than 0.5 second. 
Printing is then executed.


(smm 07/26/93)