The original set of interlocks contained in the 4MS software under Version 2.1 have been extended to include the situations when the access doors (GDU and SDU) on ISIS are unlocked, resulting in the Stepper motor drive module (SMDM) being continuously multiplexed to one specific channel. This prevents other mechanisms attached to the same SMDM from being driven until the door is once again locked, releasing control of the SMDM.

Below is a list of all the current software interlocks implemented on ISIS under Version 2.2:

a. Any Barcode read operation first disables the IPCS shutter line prior to performing the actual read (since infrared is emitted during the read), enabling the line ONLY if light tight status is true for the whole instrument.

b. The dekker slide (DEK) and slit door (SDU) are interlocked such that the dekker slide must be in position 0 before the slit door may be unlocked so as to reduce the possibility of damaging either the dekker slide/drive and/or the slit jaws.

c. The grating drives (GRB GRR), grating cells (GCB GCR) and the grating doors (GDU) are all interlocked such that the grating drive must first be rotated to its park position of 35.000 +/-2.000 degrees before the grating door may be unlocked. The grating cells may be unclamped or clamped via the red buttons located on the grating units only when the grating drive is in its park position. Finally the grating doors may only be locked if the grating cells are both clamped to prevent them being left in a dangerous state.

d. Once the Grating door is unlocked the solenoid remains continuously energised until the door is relocked. This prevents any other mechanism attached to the same SMDM from being driven and therefore interlock flags are employed to indicate this situation. The flags are cleared once the door is both closed and locked. The mechanisms associated with the same SMDM are:


e. The Slit door is the same as above while the common SMDM mechanisms are:


f. The Anamorphotic lens (ALS) and the two polarisation slides (PQW and PHW) are interlocked as they occupy the same physical space when inserted into the light beam. Either one or both PQW and PHW may be inserted together but only the ALS may be inserted on its own.


The use of the sealed vocabulary is to reduce typing errors accidentally crashing the 4MS system software. The following list of words are contained in the sealed vocabulary which is enabled on power up and are accessable through the operator's port:

M-LIST displays Monitor Mode List including types

S-LIST displays Status List

WHO displays Ethernet source and datagram

EMSG displays Ethernet datagram

SEE tabulates PRESENTSTATUS Table with labels

.SLINKS displays faulty serial links (if any)

.TIMEOUTS displays all serial link resets and timeouts

.MECHS displays all mechanisms with lower and upper limits

TRANSPARENT provides direct link to serial ports

TT short hand version

LOCAL permits direct entry of ethernet datagram

| short hand version

+FERRANTI enables continuous operation of both Ferranti

-FERRANTI disables " " " "

-ASL defaults ASL M9000 to measuring slit jaws


M9000-POSNS position update for collimators and slit jaws

WARM-START restarts system following ABORT button

SIGN-ON logs on to NIU with NET200 message to itself

NET101 resets ethernet software then signs on to NIU

RES101 Shuts system down, reinitialises tables then restarts system

BLUE displays the current blue grating position in degrees

RED displays the current red grating position in degrees

All the mechanism mnemonics:





The following suite of diagnostic words provide easy access to specific areas within the Kernel, via the operator port, to assist in both commissioning and fault finding:

WHO displays the node name and message received by the Kernel from the ethernet port. Employed for checking that the message has been passed on by the network layer as well as diagnosing Kernel processing of that message.

M-LIST displays all 6 entries in the monitor-mode request list MON~LIST along with their request type (1 or 2).

S-LIST displays all 4 entries in the write-only status (immediate and delayed) request list STATREQ.

SEE All the fields in the PRESENTSTATUS table for the specified mechanism are displayed in a tabular form. Each parameter is displayed using its correct numerical base along with its field identification label.

TIMEOUTS displays the number of resets and communication timeouts for all serial links in a tabular form, labelling each link with its corresponding module name. These values may also be transmitted across ethernet to the VAX System Computer by employing the health monitor status command, HMS200. A history may then be built up for each module, enabling suspect units to be weeded out of the system.

#SLINK requires the mechanism mnemonic number on the stack prior to executing this word. It displays the work space RAMSLINK for specified serial link. Employed when faults occur on serial link eg. #ERROR byte field can show framing, parity and overrun errors indicating wrong baudrates etc. See section on communication software.

#LINK requires the mechanism mnemonic number on the stack prior to executing this word. It displays the serial communication receive buffer for specified link. See section on communication software.

.MECHS lists all the instrument's mechanism mnemonics along with each of their corresponding minimum and maximum parameter limits. Employed as an aide-memoire.

.SLINKS displays which serial links are faulty. This automatically occurs on powerup/reset of the 4MS but may be requested at any time through the operator's port.

LOCAL Provides the ability to enter a single ethernet message (which may contain several instrument commands) via the operator port. It initially shuts the ethernet tasks down in an orderly fashion to prevent two sources of messages using the same internal buffer resources. The operator is prompted for the required message which is terminated by a carriage return, eg:

Enter Emsg : ABC101(1234)<cr>

The Kernel then processes the message in exactly the same way as for a message received via the ethernet port. Finally the ethernet tasks are reactivated followed by a NET101 execution to flush the network software layer.

Under LOCAL operation status requests (immediate or delayed) will result in status replies being sent to the node who last sent a command via the ethernet port. It is therefore advised to omit all status requests when employing the LOCAL mode.

A shorthand version is available in the form | (pipe).


requires the mechanism mnemonic number on the stack prior to executing this word. Any piggyback mechanism (see mechanism description) is first translated to its host before the SMDM protocol header is displayed, informing the operator which box# and motor# the specified mechanism is attached to. The commands required to enable the echo mode and to terminate the TRANSPARENT mode are also included:

a) Transparent to Smdm C Motor 2

To enable echo : UNSEAL

To return to 4MS : 4MS

Additional mnemonic constants are defined to gain access to the barcode reader modules (GBCRM and HBCRM) and the ASL unit (M9000). Each TRANSPARENT displays its own specific protocol header, for the barcode reader case, the mnemonics of the mechanisms attached to each channel are listed:

b) Transparent to Bcrm G

1.......... 2......... 3........... 4 .............5 .............6 ............7 ..........8

- .......FDB..... BFA.... BFB .......DEK ......RFA...... RFB......... -

To enable echo : UNSEAL

To return to 4MS : 4MS

c) Transparent to Bcrm H

1 .............2............ 3............ 4.............. 5............. 6........... 7.............. 8

GRB ......GRR..... XDB..... XDR......... -............. MFS.......-............... -

To enable echo UNSEAL

To return to 4MS : 4MS

d) Transparent to M9000

To return to 4MS : ^A

The Kernel shuts down all status MAINTAIN, JOB and ethernet tasks in an orderly fashion, then revectors the interrupt routine and enables the serial link interrupt ready for transparent operation. This state is indicated by:

Application halted

being displayed when commands may now be entered via the operator terminal.

Refer to the corresponding manuals for description of the commands available for each module.

On termination of transparent mode the interrupt routine is revectored and all the tasks are reactivated. Resumption of normal operation is indicated by the message:

Application restarted

appearing on the operator terminal.

All modules employing the 6303 processor card (SMDM, BCRM and HSM) must be correctly sealed up by their word '4MS' before returning to normal Kernel operation otherwise all subsequent communications with the module will result in continuous timeouts due to unexpected strings being received.

A shorthand version of TRANSPARENT is available in the form TT.