The IOtech Digital488 and Digital488/32/OEM are IEEE 488 to Digital I/O Interface devices, designed to facilitate communication between a system controller and digital I/O ports. These devices conform to the IEEE 488-1978 standard, often referred to as GPIB (General Purpose Interface Bus), which specifies electrical, mechanical, data transfer, and control protocols for instrumentation communication.
Function Description:
The primary function of the Digital488 and Digital488/32/OEM is to act as an interface between an IEEE 488 bus and digital I/O lines. They allow a system controller to send data to and read data from digital I/O ports, as well as manage handshake lines and service requests. The devices are microprocessor-based, utilizing a 6809 microprocessor, firmware EPROM, and static RAM for operation. A Versatile Interface Adapter generates real-time interrupts for the firmware operating system, and a TMS9914A controller handles the IEEE 488 bus interface.
Important Technical Specifications:
- Data Lines: The Digital488 features 40 data lines, programmable in groups of 8 as either input or output. Port 1 is the least significant 8 bits, and Port 5 is the most significant 8 bits. The Digital488/32/OEM has 32 data lines, similarly programmable in groups of 8, with Port 1 as the least significant and Port 4 as the most significant.
- Logic Levels: Data and handshake output lines can drive two TTL loads. Ports 1 and 2 outputs are 5 Volt CMOS compatible. All input lines are less than 1.5 TTL loads and are protected against high static voltages. Input voltages should be limited to -0.3 to +7.0 volts. All I/O lines are referenced to COMMON (Pin 50).
- IEEE 488 Address: The bus address is set via internal DIP switches (SW1-1 through SW1-5) from 0 to 30. The factory default is address 18. Address 31 defaults to 30 as it's reserved by the IEEE 488 standard.
- Output Terminators: Terminating characters (Carriage Return, Line Feed, EOI) sent on output are determined by internal DIP switches (SW1-6 through SW1-8) or can be programmed by the controller. The factory default is Carriage Return - Line Feed with EOI asserted.
- Power: User-supplied +5 volts ±0.25% at 1 amp. Mating power connector with 8-inch leads is provided.
- Dimensions (Digital488/32/OEM): 3.025 inches (width) x 3.965 inches (length) x 1.365 inches (height).
- Operating Environment: Standard: Indoor, 0° to 50°C; 0 to 70% RH to 35°C. Linearly derate 3% RH/°C from 35 to 50 °C.
Usage Features:
- Command-Based Control: The device is controlled using a set of 17 bus commands, including Bit Set (An), Bit Clear (Bn), Bus Output (Gn), Configure (Cn), Data (Dn...Z), Data Ready (Rn), End or Identify (Kn), Execute (X), Format (Fn), Handshake (Hn), Inhibit (Qn), Invert (In), Port (Pn), Service Request Mask (Mn), Status (Un), Terminator (Yn), and Test (T0).
- Flexible I/O Configuration: Ports can be configured as inputs or outputs, allowing for versatile application in various systems.
- Data Formats: Supports six data formats for input and output: ASCII Hexadecimal (F0), ASCII Character (F1), ASCII Binary (F2), ASCII Decimal (F3), Binary (F4), and High Speed Binary (F5).
- Handshake Control: Provides software control over handshake lines (Clear, Strobe, Trigger) and allows for inversion of their active states.
- Service Request (SRQ) Management: The device can generate service requests to alert the controller of various conditions, such as service input transition, EDR input transition, bus errors, self-test errors, or completion of command execution. The Serial Poll Status Byte provides detailed information on the cause of the SRQ.
- Status Monitoring: The Status command allows reading the device's current status, including configuration, error messages, data format, invert control lines, and SRQ mask.
- Address Selection: The IEEE 488 bus address is easily configurable via internal DIP switches.
Maintenance Features:
- Self-Test Function: The Test (T0) command initiates a ROM/RAM test. If the test is successful, all LEDs flash for one-half second. If it fails, the Error LED remains illuminated, and the Status command can be used to determine the cause of the error.
- Troubleshooting: In case of problems, users are advised to contact the factory service center for assistance. Many issues can be resolved through discussions with the applications department.
- Safety Warnings:
- Never open the device case while it is connected to the AC line, as internal voltage potentials exist.
- The interface is intended for indoor use only; outdoor conditions could lead to equipment failure, bodily injury, or death.
- Do not install the power supply into the interface while it is connected to the AC line.
- Inspection: Upon receipt, users should inspect the unit for any physical damage and retain all shipping materials in case a return is necessary.
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