Instrumentation Control Bus (J.Quick)

The main instrumentation bus which will be used to control digital input/output is the so-called Serial Digital Input Output bus (SDIO). This bus which relies on a serial link and a simple protocol was developed by J.Jonas of Rhodes University and is now being further developed and maintained by J.Quick at HartRAO. SDIO will be used on the NCCS through the BOCA 16 port serial interface. For details of the actual SDIO based devices see the relevant sections below.

The original SDIO concept has been adapted for use on the NCCS as follows :

1.

The RS232 protocol was converted to RS422 in order to transmit over long distances noise free.

2.

The topology of the SDIO links was converted from a daisy-chain loop to a tree so that failure of any one SDIO unit has the minimum effect on other equipment.

3.

Each tree of SDIO units is serviced by a single monolithic device server capable of handling all possible SDIO based devices.

Tasks completed:

$\Longrightarrow$

RE-DESIGN THE SDIO TO USE A RS422 TREE TOPOLOGY,

$\Longrightarrow$

BUILD SIX SDIO REMOTE UNITS AND THREE COMPUTER INTERFACES,

$\Longrightarrow$

WRITE A GENERIC DEVICE SERVER FOR SDIO.

Tasks still to be done :

$\Longrightarrow$

INTEGRATE SDIO WITH PROPOSED ALARM/LOG SERVERS.