Black Box IC026A-R2, IC026AE-R2 Controller Operation, Controller-Mode Serial to Ieee Operation

RS-232↔IEEE 488 INTERFACE CONVERTER

4.Controller Operation

4.1Controller-Mode (Serial to IEEE) Operation

The IEEE Controller mode allows a serial RS-232 or RS-422 host device to send data to a single IEEE bus peripheral or to multiple peripherals if they occupy the same bus address. Applications include interfacing a listen-only or addressable IEEE printer/plotter to a serial printer port.

Once the interface converter has initialized itself after power-on, it waits for serial input data. When received, it addresses the selected IEEE device to listen with the following bus sequence:

ATNUNL,MTA,LAG,*ATN

The data received from the serial host is placed into a circular serial input buffer. Simultaneously, characters are removed from that buffer and sent to the IEEE bus device. The serial terminator(s), if present, are not sent.

Instead, the IEEE terminators are substituted and sent in their place.

As long as the serial input buffer is not empty, the interface converter will continue to send data from it to the IEEE bus device. If the serial input buffer becomes emptied, the interface converter will command the IEEE bus device to talk if one of the talk-back features is enabled. This allows the interface converter to be used as a controller with devices, such as plotters or instruments, that return status and other information to the host computer.

When the interface converter addresses the IEEE bus device to talk it uses the following bus sequence:

ATNUNL,MLA,TAG,*ATN

The interface converter then accepts data from the IEEE device and returns it to the host until the last selected IEEE terminator is detected. The IEEE bus terminators are replaced by the serial terminators, and these are then sent to the serial host.

If the IEEE device has been addressed to talk but does not respond or finish transmission by the time additional characters are received in the circular serial-input buffer, the talk sequence will be aborted to allow additional serial information to be sent to the IEEE device.

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