DMP 110  (260-1271)             Buffer                 Faxback Doc. # 4275

Size:   1 Line

PRINTER BUFFER OPERATION

The printer's ability to temporarily store data is one of its main advantages 
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 
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 960 horizontal dot positions by 16 vertical dots as
  its printing image. In case character data is in DP or WP Mode, the data  
  received is converted to the character matrix according to the character  
  styles, elongation and/or boldface designation and stored in the buffer. In  
  the Graphics Mode, the data is stored as pattern. The character style  
  changes (elongation or boldface designation), therefore, do not cause  
  printing.

* The micro space (27 n), backspace (8 n), and dot positioning (27 16 n n)
  changes the stored dot position information (add/subtract dot position).
  These also do not cause printing.

* If the last received character exceeds the 960th dot position, the buffer is
  printed without printing the last character, and the last character will be
  printed at the start of the next line, after automatic line feed and   
  carriage return (this is called "wrap around").

* The carriage return code (13) activates to print the buffer, and the
  subsequent data will be printed at the start of the next line.

* The line feed code (10) also activates the printing. The subsequent data
  will be printed at the start of the next line.

* The carriage return only code (26) activates the printing, and the
  subsequent data will be printed over the current line.

* If buffer contains some data and the computer stops sending data for a
  second, the buffer is printed, and printing will continue from the current
  position when data is received again.

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

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


(smm 07/26/93)