DMP 300  (260-2818)    Printer Buffer Operation        Faxback Doc. # 4625

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 
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 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 
printing (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 next buffer full prints the subsequent 
characters over the current line. Otherwise, subsequent characters print
at the start of the next line.

* The line-feed code (LF = 10) automatically activates printing. If you 
select LF only in the 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 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 
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 on the 
current 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, and 27 29. Printing continues in the current line with the 
new character style.

* When the printer receives the start graphics and returns to a standard or 
condensed characters, the buffer prints. Dot graphics printing continues 
from the current character position.

* When the printer receives a start bold or end bold, the buffer prints. 
Printing continues from the current character position.

GRAPHICS MODE ONLY:

* When the printer receives the end graphics and returns to a standard or 
condensed character printing position, the buffer prints. The printer re-
turns 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 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.


(smm 07/26/93)