Advantech RS-485 user manual Introduction, Syntax

Command Set

6.1Introduction

To avoid communication conflicts when several devices try to send data at the same time, all actions are instigated by the host computer. The basic form is a command/response protocol with the host initiat- ing the sequence.

When systems are not transmitting they are in listen mode. The host issues a command to a system with a specified address and waits a certain amount of time for the system to respond. If no response arrives, a time-out aborts the sequence and returns control to the host.

Changing ADAM-5000/5000E system's configuration might require the system to perform auto calibration before changes can take effect. This is especially true when changing the range as the system has to perform all stages of auto calibration that it performs when booted. When this process is underway, the system does not respond to any other commands. The command set includes information on the delays that might occur when systems are reconfigured.

6.2Syntax

Command Syntax: [delimiter character][address][slot][channel] [command][data][checksum][carriage return]

Every command begins with a delimiter character. There are four valid characters: $, #, % and @.

The delimiter character is followed by a two character address (hexa- decimal) that specifies the target system. The two characters following the address specifies the module slot and channel.

Depending on the command, an optional data segment may follow the command string. An optional two character checksum may also be appended to the command string. Every command is terminated with a carriage return (cr).

Note: All commands should be issued in UPPERCASE characters only!

6-2 ADAM-5000