LMP 2150  (260-1272)              Buffer               Faxback Doc. # 5643

The LMP-2150's ability to temporarily store data (256 characters) 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 cer-
tain codes are received (e.g., 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 printed on the paper.

Understanding how the buffer works is important for those who wish to gain
full control of the LMP-2150.

HINTS AND TIPS ON THE LMP-2150 BUFFER

For 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.

* The next character received 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 
  (Switch 2), then the buffer is printed and the shuttle moves to the next
  Top-of-Form line.

* The Carriage Return code (CR = 13 decimal) automatically activates 
  printing.  If LF only has been selected (Switch 3), the print head is 
  moved to the start of the current line and the next buffer full will 
  print 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 (Switch 2), then the buffer is printed 
  and the shuttle moves to the next print line without a carriage return
  to the start of the line. Otherwise, the shuttle is positioned at the 
  start of the next print line.

* The print mechanism positioning sequence (27 16 n1 n2) causes printing to
  continue in the line at the dot address specified by the (27 16) command.

DATA AND WORD PROCESSING MODES ONLY:

* The backspace command causes printing to continue in the current line at 
  the dot address specified by the command.

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:

* In the description, "next line" means the new line performed by Line Feed
  operation.

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

(dtc-08/04/93)