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SEMI E30-1103 © SEMI 1992, 2003 64 Figure 4.11 Spooling State Diagram Once communications are established, the host must initiate the spool unload sequence to restore full functionality (see b elow). Since the equipment …

SEMI E30-1103 © SEMI 1992, 2003

4.11 Spooling — Spooling is a capability whereby the

equipment can queue messages intended for the host

during times of communication failure and

subsequently deliver these messages when

communication is restored. Spooling is limited to

primary messages of user-selected streams.

4.11.1 Purpose — The purpose of spooling is to

provide a method for retaining equipment message data

that might otherwise be lost due to communication

failure. The motive for producing this functionality is to

retain valuable data used to track material and to

improve product quality. The spooling capability fills a

gap in the SEMI E5 standard. In the past, without a

spooling capability, the equipment has typically

discarded messages that could not be delivered, or

turned messaging off altogether. It is intended that the

host initiate the spool unload process immediately

following the reestablishment of communications.

4.11.2 Definitions

MaxSpoolTransmit — An equipment constant

containing the maximum number of messages that the

equipment shall transmit from the spool in response to

an S6,F23 “Transmit Spooled Messages” request. If

MaxSpoolTransmit is set to zero, no limit is placed on

the messages sent from the spool. Multi-block

inquire/grant messages are not counted in this total.

OverWriteSpool — A boolean equipment constant used

to indicate to the equipment whether to overwrite data

in the spool area or to discard further messages

whenever the spool area limits are exceeded.

Send Queue — Refers to the queue into which

equipment generated SECS messages are placed in

preparation for transmission to the host.

Spool — The spool is an area of non-volatile storage in

which the equipment stores certain messages that

cannot be delivered to the host (when the equipment is

in the NOT COMMUNICATING substate of

COMMUNICATIONS ENABLED). The spool area

can be thought of as a sequential “ring” buffer. The

term spool is also used to denote the action of placing

messages into the spool area.

SpoolCountActual — A status variable used to keep a

count of the messages actually stored in the

equipment’s spool area. Multi-block inquire/grant

messages are not spooled and not included in this

count.

SpoolCountTotal — A status variable used to keep a

count of the total number of primary messages directed

to the spool, regardless of whether placed or currently

retained in the spool. Multi-block inquire/grant

messages are not spooled and not included in this

count.

SpoolFullTime — A status variable containing the

timestamp when the spool last became full. If the spool

was not filled during the last spooling period, this will

contain a time value prior to the current

SpoolStartTime.

SpoolStartTime — A status variable containing the

timestamp from when spooling was last activated.

4.11.3 Description

4.11.3.1 Spooling State Model — There are two major

states of spooling: SPOOL INACTIVE and SPOOL

ACTIVE. SPOOL ACTIVE has two components:

SPOOL UNLOAD and SPOOL LOAD. These are each

broken into substates. A description of all spooling

states, substates, and applicable state transitions

follows. The POWER OFF and POWER ON parent

states are common to all equipment subsystems. They

are shown here to illustrate the retention of spooling

context during a power down situation.

NOTE 20: Disabling SECS communications does not affect

the current spooling state since no messages are generated

until communications are subsequently enabled. Spooling is

effectively frozen in this case.

POWER OFF

The equipment has lost power for any reason (e.g.,

power failure, power switch set to off).

POWER ON

The equipment is powered up.

SPOOL INACTIVE

This is the normal operating mode. No spooling occurs.

The spool area is empty. Primary SECS-II messages are

transmitted normally.

SPOOL ACTIVE

All primary SECS-II messages ready for sending and

for which spooling is enabled (see S2,F43) are directed

to the spool area. All other primary messages, except

Stream 1, are discarded. The equipment shall attempt to

send any secondary messages that are generated and

discard these messages should the attempt to send fail.

Spool state transitions from SPOOL INACTIVE to

SPOOL ACTIVE if the communications state changes

from COMMUNICATING to NOT COMMUNI-

CATING (Communication State Transition Table, #14)

or from WAIT CRA to WAIT DELAY

(Communication STATE Transition Table, #6).

SEMI E30-1103 © SEMI 1992, 2003

Figure 4.11

Spooling State Diagram

Once communications are established, the host must

initiate the spool unload sequence to restore full

functionality (see below). Since the equipment will

deliver secondary messages, the host may inquire for

information or send commands as needed.

The SPOOL ACTIVE state has two AND states:

SPOOL LOAD and SPOOL UNLOAD. This means

that they operate independently, though sharing data

and some state change stimuli. See Section 3.1 for

explanation of state model terms and notation.

SPOOL LOAD

The SPOOL LOAD component enters messages into

the spool area. It is divided into two substates: SPOOL

NOT FULL and SPOOL FULL. SPOOL NOT FULL is

the default entry substate of the parent state SPOOL

LOAD.

SPOOL NOT FULL

As primary SECS-II messages are directed to the spool

area, the equipment shall “write” the SECS-II message

to the end of the spool. Status variables

SpoolCountTotal and SpoolCountActual shall be

incremented each time a message is placed in the spool

area.

SPOOL FULL

In this state, all of the allocated spooling area is filled.

Choice of the following options shall be controlled by

the setting of a Boolean equipment constant called

“OverWriteSpool.” The first message to be dealt with is

that which could not be fit into the spool prior to

transition from SPOOL NOT FULL (see transition

table below).

OverWriteSpool is True: The equipment deletes as

many of the “oldest” records (e.g., SECS-II messages)

contained in the spool area necessary to make space for

the new message and then adds the message. Status

variable SpoolCountTotal shall be incremented

whenever a message is submitted to the spool area.

Status variable SpoolCountActual shall be manipulated

to keep an accurate count of the number of messages

contained in the spool area. For example, if it is

necessary to delete three messages in the spool area to

spool one message, SpoolCountActual would have

three subtracted and then one added to the total.

OverWriteSpool is False: Any subsequent primary

messages shall be discarded. When such a message is

discarded, SpoolCountTotal is incremented.

SPOOL UNLOAD

The SPOOL UNLOAD component of SPOOLACTIVE

deals with movement of messages out of the spool. It

has an active substate (SPOOL OUTPUT) and a

passive substate (NO SPOOL OUTPUT). NO SPOOL

OUTPUT is the default entry substate, since the

equipment is NOT COMMUNICATING at the time

spooling is initiated. When communications between

equipment and host are restored, there is an opportunity

for the host to recover spooled messages. No action is

taken until the host initiates the spool output process

via the S6,F23 (Request Spooled Data). The host has

the option to either receive the spooled messages (see

substate TRANSMIT SPOOL) or discard all messages

in the spool (see substate PURGE SPOOL).

NO SPOOL OUTPUT

In this state, no messages are removed from the spool.

SPOOL OUTPUT

The SPOOL OUTPUT state encompasses the removal

of messages from the spool. Its substates are TRANS-

MIT SPOOL and PURGE SPOOL.

TRANSMIT SPOOL

The host elects to receive all messages contained in the

spool area. The equipment is expected to keep track of

the oldest record (i.e., message) within the spool area.

When communications are re-established with the host

and transmission of the spool area is started, the oldest

record must be the first record transmitted, then the

next oldest record, etc. There is no prioritization of

messages to be sent from the spool.

As each spooled message is successfully transmitted to

the host, it is removed from the spool area upon

successful completion of the transaction. Spool-

CountActual is decremented as each message is

removed from the spool. The equipment shall transmit

messages only from the spool area until all spooled

messages have been completely transmitted to the host.

Flow control of the spool transmit process is achieved

in two ways. First, only one open transaction on the

equipment is allowed during spool unload. Thus, if a

message requires a reply, the equipment shall wait for

that reply before transmitting the next spooled message.

Messages which require no reply may be transmitted

sequentially as rapidly as the message transfer

mechanism will allow.

The second flow control method is to allow the host to

limit the maximum number of messages sent from the

spool in response to the S6,F23 request. An equipment

constant named MaxSpoolTransmit may be set by the

host to achieve this behavior. If MaxSpoolTransmit is

set to five, for example, the equipment will send the

first five messages from the spool and then transition to

the NO SPOOL OUTPUT state, awaiting the next

S6,F23 request. There is no event report generated

when MaxSpoolTransmit is reached. The host is

responsible for determining this situation by a)

counting the messages received, b) timing out waiting

for the next message, c) inquiring to the equipment for

the curent value of the SpoolCountActual status

variable, or d) some combination of the above. If

MaxSpool-Transmit is set to zero, the spool shall be

transmitted completely in response to S6,F23.

Normal spooling continues during the spool transmit

process. If the SPOOL LOAD component should

transi-tion to SPOOL FULL, it shall not have any effect

on the SPOOL UNLOAD component. Once full, the

spool cannot make the transition back to SPOOL NOT

FULL except via the SPOOL INACTIVE state. Space

made available due to the spool unload process shall

not be used in this case.

When a multi-block message is to be transmitted from

the spool, any required inquire/grant transaction shall

be initiated. If the host’s response denies permission to

send the multi-block message, the equipment shall dis-

card that message and continue with the transmit pro-

cess. This sequence shall count as one message in the

MaxSpoolTransmit count.

There is one area where SPOOL LOAD and SPOOL

UNLOAD may interact: When the spool is full and

OverWriteSpool is True. During the spool transmit pro-

cess, spooled messages are being removed and new pri-

mary messages are being written to the spool. These

new messages are overwriting the oldest messages

available, unless the unload process has freed sufficient

spool space. There is a possibility that the unload and

overwrite processes may compete for control of the

same message area. For example, if the spool holds

messages ABCDE, with A oldest and E newest, A

might be sent to the host, B (and the space from A)

overwritten by the new message F, C sent to the host, D

and E (and the space from message C) overwritten by

G, etc. The loss of continuity may be “disorienting” to

the host program receiving the messages. It is expected

that the unload process will be fast relative to the

generation of new messages, so that this occurrence

will be rare.

Should a communication failure occur during the spool

transmit process, spooling shall continue as before the

transmit process began. However, the spool unload

sequence shall terminate (i.e., transition to NO SPOOL

OUTPUT will occur — see transition table below).

PURGE SPOOL

The equipment shall discard all messages in the spool

and, when the spool is empty, zero SpoolCountActual.