Preamble or Postamble Selection
Preambles and Postambles are composed of up to four ASCII charac- ters. Each ASCII character is encoded as two hexadecimal numbers. Use the Hexadecimal Conversion Table in Appendix A to look up the hexadecimal equivalent.
| If you select a Preamble or a Postamble you must scan | |
| four ASCII characters, even if the Preamble or Postamble | |
| is less than four characters in length. This is done by | |
| scanning in null (NUL) characters for the additional char- | |
NOTE | acters. For example, if your Preamble is “AB” (in ASCII | |
code), scan A, then B, then two null characters, or 4,1, 4,2 | ||
| ||
| 0,0 0,0 hexadecimal. |
Preamble
A Preamble is a string of characters that prefixes a message that is transmitted to the host. The sequence and number of characters in a Preamble is determined by the type of host system. Although not all systems require a Preamble, those which do will only receive mes- sages with the correct Preamble. The maximum preamble length is four characters.
KA
Preamble = None*#
KB
Enter Preamble
IMPORTANT
Scan Enter Preamble to enter a Preamble, then refer to the Hexadecimal Table in Appendix A.
Postamble
A Postamble is similar to a Preamble, except that it appended to the message which is transmitted to the host. Its maximum length is also four characters.
06656 | 29 |
