Control of a pulse height analyzer using an RDX workstation

The Nuclear Chemistry Division of Lawrence Livermore National laboratory is in the midst of upgrading its radiation counting facilities to automate data acquisition and quality control. This upgrade requires control of a pulse height analyzer (PHA) from an interactive LSI-11/23 workstation running RSX-11M. The PHA is a micro-computer based multichannel analyzer system providing data acquisition, storage, display, manipulation and input/output from up to four independent acquisition interfaces. Control of the analyzer includes reading and writing energy spectra, issuing commands, and servicing device interrupts. The analyzer communicates to the host system over a 9600-baud serial line using the Digital Data Communications link level Protocol (DDCMP). We relieved the RSX workstation CPU from the DDCMP overhead by implementing a DEC compatible in-house designed DMA serial line board (the ISL-11) to communicate with the analyzer. An RSX I/O device driver was written to complete the path between the analyzer and the RSX system by providing the link between the communication board and an application task. The I/O driver is written to handle several ISL-11 cards all operating in parallel thus providing support for control of multiple analyzers from a single workstation. The RSX device driver, its design and use by application code controlling the analyzer, and its operating environment will be discussed