TransAct Epic Edge, Руководство по интеграции OEM

Страница: 69 / 191

100-14444 Rev B August 2018 Page 59
Resetting the Printer
Each print job should begin with a printer reset command. This ensures that the printer
always begins in a known state.
The command characters used to reset the Epic Edge™ are
ESC (decimal value 27)
and * (decimal value 42).
Command Parameters
When sending a command, all of the command characters and parameters that make up
a command must be sent. This is especially important when using the bar code and
graphics commands. Sending too few characters to fill the required parameters for a
command will either cause the command to fail or result in subsequent data being lost.
Character Evaluation
Most of the parameters that are sent to the Epic Edge™ Printer are evaluated based on
their decimal value.
Some commands accept parameters by either their decimal value or the representative
character. For example, the set print orientation command (
GS V
) interprets both a
NULL (ASCII decimal value of 0) and the ‘0’ character as meaning the same thing.
16-bit Character Parameters
The maximum value a single 8-bit character can represent is 255. Some commands,
though, can take values that are greater than 255. The set horizontal starting position
command (
ESC X ), for example, specifies a distance (in dots) that the next text object
will print from the left margin. Because a dot is only 1/11.4 of a millimeter, a value of 255
would place the object only a little over 22 mm from the left margin. To allow for longer
distances to be specified, two 8-bit characters are used to specify the value, by
combining them into one 16-bit character. Though the calculations are all done within the
Epic Edge™ Printer, it is important to understand how the characters are handled.
For two specified 8-bit parameter values
n1
and
n2
, the resulting 16-bit value is
computed as follows:
Value = ( n1 * 256) + n2
In other words, the decimal value of the first character that is sent (
n1 ) is multiplied by
256, and then the decimal value of the second character sent ( n2 ) is then added to this.
To send a value under 256 to a command that takes the
n1 and n2 parameters, simply
send the first character with a 0 value. For values greater than 255 but less than 512, the