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ASCII Input Module

The Niobrara AIM4 is a SY/MAX® compatible register rack module that serves as a co-processor for ASCII data inputs to a programmable controller system through the register bus and as an output multiplexer to drive multiple ASCII peripherals from a single SY/MAX communication port. Additionally, there are 16 fixed polling strings per port which may be sent out periodically for prompting external devices without PLC intervention.

The AIM4 accepts ASCII coded serial data inputs on up to four data ports and translates the ASCII character stream to PLC register values. Pre-processing of data by the AIM4 can include ignoring certain characters, recognizing delimiters, pattern matching, and masking or modifying ASCII strings before conversion to integer, BCD, floating point, or other register formats. Processed data is transferred to the attached PLC through rack addressed dual-port memory. A copy of the backplane registers is available through the Print/Prog port for register reads from external devices such as operator interfaces without using a PLC comm port. The AIM4 is best suited for serial protocols without error checksums. If checksums are required in an application, use the UCM4.

AIM4 processing behavior is determined by a set of setup registers which may be configured or modified by SY/MAX writes or by using AIM4SW, NR&D's configuration software, which is provided free of charge with the unit. From the processor point view, the module is like any input module. A SY/MAX RS-422 port is needed only when it is desired to drive output devices from print rungs or to modify setup registers "on the fly".

Receive Input From:

  • Bar code scanners
  • Magnetic card readers
  • Keyboards
  • Scales
  • PID controllers
  • Intelligent meters
  • Other intelligent devices
Output To:
  • Parallel printers
  • Serial printers
  • CRTs
  • Message displays
  • Other intelligent devices


The AIM4 PLUS is Niobrara's second generation ASCII input module. The AIM4 PLUS has all of the functions of the original AIM4 and new features not found in the original module: the ability to use PLC register values in output strings, the ability to trigger output strings from a rack register, and the ability to terminate input messages by programmable character count or by intercharacter timeout.

Output messages are controlled by programming special character sequences in the polling query strings; in this manner register values can be inserted into an output query to provide printing capability without a direct serial connection to the processor. Each of the four ports has a dedicateed rack register to control the output of the port's 16 polling strings. This control feature allows printing from a remote rack containing an AIM4 PLUS.

The ability to terminate input messages by character count or intercharacter timeout is useful in applications where the peripheral device being interfaced does not supply a terminator character. Input messages are processed identically by the AIM4 PLUS whether terminated by terminator character, character count, or intercharacter timeout.


Dimensions: Standard SY/MAX register module. 1.5" wide by 13" tall by 6.5" deep. Approximately four pounds net. Rugged welded steel enclosure with baked on finish. All connectors and indicators are front mounted except the SY/MAX bus card edge connector on the back.

Power Requirements: From SY/MAX bus: 5 volts, 1.5 A.

Serial Ports: Four serial data I/O ports. 50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14,400, or 19,200 baud; 7 or 8 data bits; odd, even or no parity; 1 or 2 stop bits. AIM4-3S: RS-232; DB9 male connectors with screw lock posts. AIM4-3M: RS-422/485, 2- and 4-wire compatible; DB9 female connectors with slide lock posts.

Print/Prog Port: SY/MAX compatible RS-422 with same pinout as SY/MAX processor. DB9 female connector with slide lock posts. 300 to 9600 baud; even parity.

Indicators: LED Transmit, Receive, Terminator, and Pattern indicators for each serial port. Sixteen total indicators.

Rack Addressing: Configurable from 1 to 2,048 registers.

Setup Registers: Processor equivalent registers store the configuration of the unit. These registers are maintained by AC power when present, by power supply when mounted in rack, and by internal capacitor for up to one week when removed from rack.


The AIM4 PLUS is available as:

AIM4-3S with 4 RS-232 ports and 1 Print/Prog port
AIM4-3M with 4 RS-485 ports and 1 Print/Prog port

Effective 19 March 2008 - Specifications subject to change without notice.