ICS ELECTRONICS 4809A, Instruction Manual

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General Information
1.1 INTRODUCTION
This section provides the specifications for ICS's Model 4809A, 4819A
4829A and 4899A GPIB<->Modbus Interfaces and their accessory items.
Models 4809A, 4819A and 4829A are PC board assemblies designed for
mounting inside another piece of equipment. The Model 4899A is an en-
closed Minibox™ product designed for bench top use with other equipment.
All three products are functionally equivalent. The manual describes the
units' functions by referring to the 4899A but, wherever the text refers to the
Model 4899A, it also applies to the other models unless otherwise stated.
Any model differences are noted in parenthesis or in separate paragraphs.
1.2 DESCRIPTION
The Model 4809A/4819A/4829A/4899A GPIB<->Modbus Interfaces are
IEEE-488.2/GPIB to Serial Interfaces with special firmware to control
Modbus RTU Slave devices from the GPIB or HP-IB bus. They let the user
send simple commands with ASCII values over the GPIB bus to control
and query slave Modbus devices. Each interface converts GPIB commands
into the Modbus protocol and adds the CRC checksum to make a complete
Modbus RTU message. The messages are sent serially over a RS-232 link
or over a RS-485 network. Responses are checked and valid response data
from a query is returned to the GPIB bus when the 4899A is next addressed
to talk. The 4809A and 4899A handle both RS-232 and RS-485 Modbus
devices. The 4819A handles only RS-232 devices while the 4829A handles
only RS-422/RS-485 devices.
The units contain a number of advanced features that increase their flex-
ibility and simplifies their use in system applications. All have IEEE-488.2