DMP 430  (260-1267)              Buffer                Faxback Doc. # 4572

The DMP-430'S ability to temporarily store data 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 certain
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 dumped to paper.

Understanding how the buffer works is important for those who wish to gain
full control of the DMP-430.

HINTS AND TIPS ON THE DMP-430 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 unless Switch
  #1-2 is set to ON (CR only.  If different character widths have been used
  on the same line, the last character added may exceed the dot count.  The
  buffer is printed without this last character.

* 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 (Switch
  #1-8), 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 Print Head is positioned 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 Carriage Return only has been selected (Switch 1-2), 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) automatically activates printing.  If LF
  only has been selected (Switch 1-8), then the buffer is printed and the
  Print Head moves to the next print line without a carriage return to the
  start of the next line.  Otherwise, the Print Head is positioned at the
  start of the next print line.

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

* The Head Positioning sequence (27 16 n1 n2) prints the buffer.  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
  current 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, 27 31, 27 32.  Printing continues in the
  current line with the new character style.

* Dot graphics printing continues from the current character position.

* When a start Bold or end Bold is received, the buffer is printed.

* Bold printing continues from the current character position.

* When a start double height, super/subscript, italics, microfont,
  compressed correspondence, proportional quality 12 CPI, or compressed
  code is received, the buffer is printed.

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 1: In the description, "next line" means the new line performed by a
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.

NOTE2: Repeat data can cause a buffer full condition, as well as an
over flow by single characters.

HEX PRINT MODE

* The DMP-430 is capable of printing hexadecimal values for data that is
  transmitted to it.  "Hex Print Mode" is useful for checking exactly what
  information is being received by the Printer.

* To implement this function, turn on the power to the Printer while
  simultaneously holding down the FORM FEED and LINE FEED switches.

* Before printing, be sure that 15" wide paper is loaded in the Printer to
  avoid printing on the platen.  Then press the ON-LINE button and run the
  program that you want to check.

(dtc-07/27/93)

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