LIMS 244 Driver -- What are its benefits?
by Stuart Baker
Attention all LIMS users, starting with release 1.9.0 of LIMS 2000, you can put the many rumors about the 244 driver to rest. All known problems with the 244 driver have been fixed. For interactive use, the 244 driver is now fully functional! Not only does this driver bring new functionality to your LIMS software, but you now have all of the BIOC features available at MTM without the need to switch drivers. So, what is the 244 driver and what does this all mean to the typical LIMS user? This article addresses these questions.
The LIMS interactive environment has long used the 241 driver to support its functions. The interactive mode uses fields for input much like a block mode Reliance screen, except that the terminal is running in conversational mode. The standard OS/32 drivers like BIOC and CTD do not lend themselves to this type of input. The basic problems are:
The 241 driver works well in the LIMS interactive mode, so why develop another custom driver? Simple, the standard features of drivers like BIOC and CTD offer many editing features not available in the 241 driver. In addition, many programs that require the support offered by the standard OS/32 drivers will not function with the 241 driver. If a LIMS site wishes to use these programs, they must sysgen both the BIOC driver and the 241 driver for each port. They must then use a program like SDECM to switch between the two drivers. Sysgening two drivers for each port not only complicates the sysgen process, but the resulting operating system uses a lot of extra memory (a scarce resource on many systems). In fact, if your system has a large number of terminals, you might not be able to include two drivers for each port, because the 64KB pure code limit would be exceeded. In addition to increasing the operating system size, you must use more memory for SDECM to allow you to switch between drivers. The 244 driver solves all of these problems.
The 244 driver is based upon the standard BIOC driver. You might say that this is a split personality driver. It looks and acts like the standard BIOC driver when used with applications like MTM, PASSPORT, KERMIT32 and XMODEM32. But, when it is used with the LIMS software, its personality changes to allow field editing. This split personality is accomplished through the SVC1 extended options. The LIMS software determines when it is using the 244 driver and sets bits in the extended options word to select the LIMS mode of the driver. Since other programs do not set these bits, the driver functions as a standard BIOC driver for all other software packages. This split personality mode eliminates the need to sysgen two drivers for each port and eliminates the need to use SDECM to select the desired driver. You can now go from running LIMS to running PASSPORT, or any other program that requires the BIOC driver, without any extra hassle.
When the 244 driver is in LIMS mode, it brings most of the BIOC editing features to the data entry mode of the LIMS software. The first difference a LIMS user will notice is that when they select a non-numeric field for edit, the cursor is positioned at the end of the line. The LIMS software uses the BIOC alter mode to allow editing of existing data. This makes simple changes a breeze, since you no longer need to re-enter the entire line. Most of the BIOC editing commands are available in the LIMS mode. The following table lists all of the BIOC editing keys and indicates the functions that are supported (Sup field = Y) in LIMS mode.
When you look at the list of supported BIOC features, you will notice that all of the line editing capabilities are available (except Ctrl-R). The features that are not supported are special purpose and we felt that their presence would cause confusion in a data entry intensive environment. If you attempt to use one of the disabled features, you receive a beep. Remember, if you ever place the 244 driver into a mode that is not desired, Ctrl-N resets the driver to its defaults.
In addition to disabling some of the BIOC commands, the LIMS mode also changes the way some editing functions work. Most notable, the backspace (Ctrl-H), delete character (Ctrl-_) and cancel line (Ctrl-X) all use underline as the fill character instead of a space. Also, LIMS mode reads do not complete on buffer full, they require a carriage return (Ctrl-M) to terminate them. This last change keeps you in the current field until you explicitly end the edit, giving a consistent feel to the data entry process.
Does all of this mean the 241 driver is dead? Well no, not quite. The 244 driver is capable of handling all interactive modes without problem. With its typeahead feature, it will also handle devices with ease. Regrettably, the LIMS support function DEVIO, used to control devices, has not been upgraded to recognize the 244 driver. It only works with the original 241 driver. This means that user written applications that use DEVIO still require the 241 driver. Because of this restriction, it would be a good idea for user written applications to use SYSIO calls. If your applications use the DEVIO routine, you will still need to include the 241 driver in your system to control devices.
It is my understanding that the LIMS CLAS software uses SYSIO calls. It should therefore work with the 244 driver, but I do not know anyone that has tried it. If anyone has experience with the CLAS software and the 244 driver, please contact me. Now that the problems with the 244 driver have been resolved, it sure would be nice if the rest of the LIMS software were upgraded to fully support the driver for all applications (hint, hint PE). At this time, I highly recommend using the 244 driver for all interactive terminals, even if you do not need to access packages like PASSPORT, KERMIT32 and XMODEM32.
Well that about does it for this issue. I am looking forward to meeting new people at Interchange 92. Start making your plans now so we have a good turnout.
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