All network commands are in the form :- XXXaaa  Where XXX is the mechanism mnemonic and aaa the command.

100 - STOP- stop movement

101(n) - MOVE - move to position n

102 - INITIALISE - initialises mechanism to datum position.

180 - READ BARCODES - (not yet implemented on ISIS )

181 - REPROGRAM SMDM - reprograms battery backed RAM on SMDM processor board.

200 - IMMEDIATE STATUS REQUEST - returns current status of mechanism immediately.

201 - DELAYED STATUS REQUEST - returns status of mechanism when move is complete.

Returned status will be in the form :-


Command errors :

01 Mechanism busy - Previous command still in progress.

02 Out of range - The parameter supplied with the command is outside the defined range.

03 Not used

04 Invalid format - The last command was incorrect.

05 Table full - can't fit on monitor mode list Overflow of monitor mode list table.

06 Invalid function - Function not allowed for this mechanism (eg. not xxx101, xxx200 etc)

07 Operation cancelled - mechanism in interlocked state

08 Not on monitor mode list.

Mechanism errors :  (values in hex)

01 Mechanism timeout - The mechanism failed to reach the requested position in the maximum time allowed.

02 Communications time - The 4MS failed receive a valid response from the SMDM for this mechanism.

03 Undefined position The mechanism position does not conform with the requested position. After initialisation, this means the datum bit is no longer set. For encoded mechanisms this means that the encoder reading differs from that requested by an amount greater than the allowable tolerance.

04 Un-zeroed mechanism - The command was disallowed because the mechanism must first be initialised.

05 Wrong SMDM - The 'name' returned in the SMDM status is incorrect.

06 Invalid SMDM data - The status received from the SMDM contained one or more incorrect characters.

07 Wrong ferranti encoder

08 Aborted

09 Unreliable barcode or ferranti encoder

0A Barcode head absent

0B Barcode misaligned

0C SMDM module busy - The SMDM rejected the command from the 4MS because it had not completed the previous command.

0D SMDM out of range - The SMDM rejected the command from the 4MS because the required move would take the step count outside of the SMDM limits.

0E SMDM invalid motor number - The SMDM rejected the command from the 4MS because the motor number requested was not in the range 1-4.

0F SMDM not initialised - The SMDM rejected the command from the 4MS as the mechanism must be initialised before an INDEX is allowed.


11 SMDM limit switch activated - The SMDM rejected the command from the 4MS because the limit switch(es) for that mechanism is/are active.

12 SMDM cycle not permitted - (polarisation unit).

13 ASL data invalid

FF More than one of the above errors are present.