THE CPL PROTOCOL 6 - 1
6 THE CPL PROTOCOL6.1 INTRODUCTION
The oscilloscope can be controlled via the RS-232 serial interface using the
Compact Programming Language (CPL) protocol. In this protocol a small but very
powerful set of commands is defined.
The main characteristics of the CPL protocol:
It is kept simple and straightforward and is fully tailored to use simple
communication facilities like those of BASIC.
Special emphasis is put on the ease of programming:
- easy input format with a ’forgiving’ syntax:
Commands always consist of two characters that can be upper or lower
case.
Parameters that sometimes follow the command may be separated from
it by one or more separation characters.
- strict and consistent output format:
Alpha character responses are always in UPPERCASE.
Parameters are always separated by only one comma ("," = ASCII 44).
Responses always end with a carriage return (CR = ASCII 13).
- synchronization between input and output
After receipt of every command, CPL returns an acknowledge character
and a carriage return (CR = ASCII 13), to indicate reception and/or
execution of the command.
Commands
All commands consist of a header of two alpha characters. Some of the
commands are followed by parameters to give the oscilloscope more information.
The parameters are separated from one another by a PROGRAM DATA
SEPARATOR <pds>. At the end of the complete command (i.e., header and
parameters) comes the PROGRAM MESSAGE TERMINATOR CR. After the CR
is recognized by the oscilloscope, the command will be executed. Then an
<acknowledge> and CR is sent to signal the end of the command processing.