ICS ELECTRONICS 4809A, Instruction Manual

Page: 52 / 131

3-1
3
3
Operation
3.1 INTRODUCTION
This section describes how the 4809A, 4819A, 4829A and 4899A interfaces
operate and how they control Modbus RTU controllers from the GPIB bus.
This section also describes the SCPI commands used to configure and control
the units. Wherever the text refers to the Model 4899A, it applies equally
to the Models 4809A, 4819A, and 4829A unless otherwise noted.
3.2 OPERATION
3.2.1 Basic Operation
The 4899A is a GPIB-to-Serial Interface with special firmware that converts
GPIB commands into Modbus RTU packets to communicate with Modus
devices. The 4899A responds to three types of commands:
1. IEEE-488.2 Common Commands in Table 3-2. These include the
*IDN? and *ESR? queries and the *SAV 0 save command.
2. SCPI Commands in Table 3-3 are for setting internal values such as
the GPIB address, serial parameters like baud rate and configuring the
Status Reporting Structure.
3. Modbus Commands in Table 3-5 for communicating with Modbus
device(s), setting the 4899A's serial timeout and reading the Modbus
Error Register.
Any commands that end in a ‘?’ are a query and the 4899A responds by out-
putting the response on the GPIB bus the next time it is addressed as a talker.
Any 4899A parameter settings will be lost when the unit is power cycled
unless the 4899A's configuration is saved with the *SAV 0 command.