Specifications

The D1000 modules operate with a simple command/response protocol to
control all module functions. A command must be transmitted to the module
by the host computer or terminal before the module will respond with useful
data. A module can never initiate a communications sequence. A variety of
commands exists to exploit the full functionality of the modules. A list of
available commands and a sample format for each command is listed in
Table 4.1.
Command Structure
Each command message from the host must begin with a command prompt
character to signal to the modules that a command message is to follow.
There are four valid prompt characters; a dollar sign character ($) is used to
generate a short response message from the module. A short response is
the minimum amount of data necessary to complete the command. The
second prompt character is the pound sign character (#) which generates
long responses (will be covered later in this chapter). The other two prompt
characters: left curly brace ({ ) and right curly brace ( }) are part of the
Extended Addressing mode described in chapter 10
The prompt character must be followed by a single address character
identifying the module to which the command is directed. Each module
attached to a common communications port must be setup with its own
unique address so that commands may be directed to the proper unit.
Module addresses are assigned by the user with the SetUp (SU) command.
Printable ASCII characters such as ‘1’ (ASCII $31) or ‘A’ (ASCII $41) are the
best choices for address characters.
The address character is followed by a two-character command that
identifies the function to be performed by the module. All of the available
commands are listed in Table 4.1 along with a short function definition. All
commands are described in Chapter 4. Commands must be transmitted as
upper-case characters.
A two-character checksum may be appended to any command message as
a user option. See ‘Checksum’ in Chapter 4 .
All commands must be terminated by a Carriage Return character (ASCII
$0D). (In all command examples in this text the Carriage Return is either
implied or denoted by the symbol ‘CR’.)
In addition to the command structure discussed above there is a special
command format called Extended Addressing. This mode uses a differ-
ent prompt, either '{' or '}' to distinguish it from the regular command
syntax. The Extended Addressing mode is described in chapter 10.
Chapter 4
Command Set