4.9 SIGNALS

4.9.1 Signal Naming Conventions

Signal naming conventions are (will be) defined in the Electronic Design Specification [10]. Example: ADPAOVTMPI for the overtemperature input of the power amplifier of the adapter. Signal names shall be in UPPER CASE only.

4.9.2 Signal Configuration

The LCC functions ioConfigAnalog and ioConfigDigital are used to configure signals connected to a LCU, e.g makes a connection between a logical name corresponding to a database address and the physical board and I/O pins. The signal configuration is normally done at startup of the system and can be done in three different ways

1. Through a VxWorks shell script. This is simple to write, but has the severe disadvantage that there is no error checking or conditional execution possible

2. Through an engineering user interface script. This is simple to write and allows stopping of the execution on an error. Disadvantages are:

· it requires manual intervention to start

· it is fairly slow

3. Through a VxWorks function. This takes more effort to write, but it can provide good error checking, can be started from an application and executes fast.

During development it is recommended to start with a VxWorks script or an engineering user interface script, and when the configuration works, replace it with a VxWorks function.

4.9.3 Signal Database Image

LCC can handle analog and digital I/O signals with the use of the ESO standard I/O boards.

Each I/O signal needs an image in the database, a database point containing two attributes: the value and the status of the signal, see also the LCC User Manual [2]. This image is updated when reading or writing to the signal.

WARNING: Input signals are not read when reading the database image and outputs are not set when writing the database image.

The database image is updated when using the LCC I/O functions, ioReadSignal, ioWriteSignal, ioSetBit, ioClearBit, ioChangebit, ioPulsebit and the corresponding function using direct addressing, ioDxxx.

4.9.4 Signal Monitoring

LCC provides signal monitoring. Every signal on which a process has attached an event will be monitored by LCC, e.g. LCC will read the signals periodically and update its database image. The monitoring period can be configured with the function evtSetSampleRate.

The scan system on the LCU attaches events to all attributes which are scanned on change (SRBX mode). This means that signals which are scanned in SRBX mode from an LCU are also monitored by LCC.

Additionally it is possible to monitor signals on which no process has attached an event through the function ioStartSampling.

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