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THE CPL PROTOCOL 6 - 1
6 THE CPL PROTOCOL
6.1 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.
Notes: - Literal characters are placed between double quotes, e.g. "AS".
- Literal characters may be specified in upper and lower case.