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SEMI E32-0997 © SEMI 1994 , 1997 9 commit follows an y setup activities a nd coincide s with entry to t he HANDOFF state. For example, an AGV may not be allowed to commit until it ha s moved to the point of transfer. The…
SEMI E32-0997 © SEMI 1994, 1997 8
It is important to note that the attribute of “full” or
“empty” belongs to a location rather than a port. A port
that has just received a transfer object may be able to
receive another immediately. Likewise, a port that has
sent a transfer object may have more material available
to send.
3.3 Compliance — Compliance to this standard
includes adherance to all stated requirements in this
document. This includes all defined messages services,
state models, and communications scenarios.
This standard may be divided into two parts:
• Material Movement Macro Level, and
• Material Movement Micro Level.
An equipment may be compliant to one of these parts
without the other. Details of compliance to each of
these parts are defined in the body of this document.
4 Macro Level
The set of host<->equipment interactions needed to
facilitate a transfer is called the macro level. These
interactions concentrate on the definition of the transfer
specification, and leave the details of the physical
transfer to the micro level interactions.
In addition to the services defined in Section 4, the
GetAttr service defined by SEMI E39, Object Services
Standard, is supported by this standard. The definition
for the GetAttribute service defined in Section 4 will be
removed and no longer supported in 1998.
4.1 Macro Level Concepts — The macro level is
designed with the intent of creating a widely applicable,
host coordinated material movement capability. The
result is a sequence of interactions from host to
equipment that is used to accomplish the coordination
of material movement required on the manufacturing
floor.
The elements of material movement common to all
transfers make up the framework. Other elements which
differ from implementation–to–implementation are
pushed, as much as possible, into the data portions of
communications. The common elements identified are
as follows:
• The host is responsible for designating the transfer
partners which are compatible for transfer.
• The host must supply the necessary information for
the transfer to each partner.
• Once transfer is defined, the responsibility moves
to the transfer partners, especially the designated
“primary” partner
3
. The host may monitor the
3 See the definition for “primary transfer partner” in Section 4.1.1.
transfer, but leaves the details to the transfer
partners.
• The transfer partners inform the host of milestones
during the process and of process completion.
Some of the elements which are more implementation-
specific are:
• Which partner is the sender and which is the
receiver of material. This has no intrinsic
relationship to other details, such as the selection of
the primary transfer partner.
• Whether a transfer partner is passive or actively
participates in the transfer. This also becomes a
data issue.
• The method (mechanism) of an interactive transfer.
This may vary depending on the transfer partners'
capabilities and system design. Interaction with
different partners may require different methods.
Transfer recipes containing this information may
be specified by the host as a part of the transfer
specification.
The host must have some knowledge of the capabilities
of the transfer partners it designates to perform a
transfer. It must understand which partners are
compatible. If compatible, it must know the proper role
for each partner of the transfer and what methods must
be used. If an interactive transfer is warranted, the host
must be able to determine which partner should be the
primary. Definition of the mechanism for such
determinations by the host is beyond the scope of this
document.
4.1.1 Macro Level Definitions
Abort — The immediate termination of an active job,
including a complete stop of all transfer job-related
movement. An abort may be initiated by the host (and
optionally by the operator). An abort by the host is
directed at a transfer job, not at an individual atomic
transfer. When told to abort, a transfer job shall, in turn,
abort its atomic transfers. The abort command is
intended to be used only in situations where there is risk
of material or hardware damage.
Allocate — The formal reservation of an entity's
resources for a specific purpose. In this document, it
refers to the reservation of an equipment's resources for
a specific transfer job or atomic transfer. Allocation of
needed material locations for a transfer job occurs just
prior to that job becoming active. Allocation of required
port-related resources occurs just prior to the start of an
atomic transfer.
Commit — The commit by the equipment indicates a
readiness to begin the actual material handoff. The
SEMI E32-0997 © SEMI 1994, 19979
commit follows any setup activities and coincides with
entry to the HANDOFF state. For example, an AGV
may not be allowed to commit until it has moved to the
point of transfer. The point at which an equipment may
commit is equipment-specific. There is a separate
commit for each atomic transfer in a job.
Deallocate — The release of allocated resources. In this
document, it refers to the equipment's release of the
resources reserved for a transfer job or an atomic
transfer.
Port Resources — Equipment-controlled mechanisms
that serve a port. An example of a port resource is a
cassette indexer that changes to elevation of the
material location. A port resource is available only to
the atomic transfer that has allocated that port.
Primary Transfer Partner — The partner that controls
the micro level transfer and that would receive the
optional host command to initiate the transfer. The
primary transfer partner shall always be an active
partner for the transfer. For an interactive transfer, the
nature of the transfer partners may determine which
should be primary. Otherwise, the host may choose.
Restore — An operation associated with a transfer job
which causes the resources used by that job to be
returned to the preferred idle conditions (e.g., port
access door closed). When a transfer job involves
multiple ports on an equipment, restore activities are
done on a port-by-port basis as each port is no longer
needed by the transfer job.
Secondary Transfer Partner — The opposite of the
primary transfer partner. This partner is either passive
during the transfer or is controlled by the primary
transfer partner. If active, this partner shall await
communications from the primary partner before acting
(see micro level).
Setup — A process associated with an atomic transfer
that causes the port resources to achieve required pre–
transfer conditions (e.g., port access door open).
Stop — A command available to the host that causes an
orderly termination of a transfer job. Upon receipt of a
stop command, the equipment shall complete all
currently active atomic transfers, execute the “restore”
process, and then terminate.
4.1.2 Atomic Transfer — An atomic transfer is the
handoff of a transfer object from one equipment to
another. This is the fundamental building block of
material movement. An atomic transfer includes the
minimum number of physical participants in the move:
one sender and one receiver. Thus, only one change of
ownership shall occur in an atomic transfer. All
transfers required in practice can be constructed as a
series of atomic transfers. A set of atomic transfers
combined to make a complex but cohesive transfer is
called a compound transfer.
4.1.3 Compound Transfer — On the factory floor,
many material transfer situations will require multiple
atomic transfers. For example, the host may determine
that a material carrier needs to be moved from
equipment “X” to equipment “Y” by transfer agent “T.”
To accomplish the transfer would require two atomic
transfers, first “T” acquires the carrier from “X,” then it
delivers it to “Y.” A compound transfer might involve
several equipment and include parallel as well as
sequential execution of atomic transfers.
4.1.4 Parallel Transfers — Each port on an equipment
is a separate entity. It is possible, within the limitations
of the equipment and transfer agents, to execute parallel
transfers involving separate ports on an equipment.
These parallel transfers may be with the same transfer
partner, or with multiple partners. There are no inherent
restrictions to a transfer job simultaneously executing
multiple atomic transfers on an equipment. If an
equipment's ports are static (i.e., always passive), the
equipment should allow parallel transfers. If the ports
are dynamic, there may be some sharing of resources
which could limit this (e.g., use of the same robot arm).
An equipment is not required to allow parallel transfers.
4.1.5 Transfer Recipe — The transfer recipe is an
element of the transfer specification. The scope of a
transfer recipe is one atomic transfer. A transfer recipe
may contain information defining the following aspects
of a transfer:
• setup/restore operations,
• sequence of handoff operations (see micro level),
• micro level commands to be issued by the primary
partner to the secondary transfer partner,
• parameters relating to the transfer.
Thus, the host may use the transfer recipe to
communicate the details that make it possible to prepare
for and carry out the micro level transfer.
Use of transfer recipes is not a requirement. However,
these recipes provide for dynamically “programming”
an equipment to interact properly with what may be a
completely different type of equipment. For instance, it
may be possible to “teach” one transfer partner the
proprietary commands that the other partner
understands by embedding those commands in a
transfer recipe. During the transfer, the primary partner
could issue those commands at the proper time using
standard micro level messages (see Section 5).
Transfer recipes should be created and managed
according to applicable SEMI standards and in a similar
SEMI E32-0997 © SEMI 1994, 1997 10
manner to other types of recipes on the equipment (e.g.,
process recipes).
4.1.6 Transfer System Controller as Transfer Agent —
A transfer agent is an entity to which transfer-related
commands are given in order to carry out transfer jobs.
A transfer system, which might include several material
transport devices, can be described the same way.
However, there are some important differences.
There are a number of ways that a host could view a
transport system, including:
• as a single transfer agent with numerous ports,
• as a single transfer agent with a single port and
numerous internal locations,
• as multiple logical transfer agents with their own
ports, or
• as the set of real transfer agents that the transfer
system controls.
The transfer system may conceal from the host the
various internal operations (e.g., handoffs, travel paths)
that it uses to complete a transfer. It may even hide the
actual physical location (or series of locations) and
provide a logical location for host reference.
4.1.7 Transfer Job — The host's material transfer
objectives are defined in a transfer job. This transfer job
may be a single atomic transfer or a compound transfer.
A compound transfer job consists of multiple atomic
transfers grouped together to accomplish a more
complex objective. A typical compound transfer may
also be accomplished by creating a separate transfer job
for each required atomic transfer. The decision to group
atomic transfers into a transfer job is application-
dependent.
The key advantages to the use of compound transfer
jobs are the reduction of the communication overhead
to the host and the streamlining of the transfer process.
The communication overhead is reduced by the fact that
the host can define a number of atomic transfer
operations with a single message to the equipment. The
equipment are not required to wait for host commands
between these atomic transfers.
The process is streamlined by virtue of the removal of
redundant physical activities during the transfer job.
Total setup and restore time for a port may be reduced
if the setup for consecutive atomic transfers is similar.
One example of streamlining would be the “exchange”
of carriers between equipment, where a transfer agent
might bring an empty carrier to replace a full carrier on
the “output port” of a machine. If the port has a door
that is opened during transfer preparation and closed
during the restore phase, the door would be better left
open for both atomic transfers. Upon completion of the
removal of the first transfer object, rather than close the
door, the new transfer is begun and the door left open.
The two atomic transfers would thus be executed as one
smooth “swap” transfer without wasted time.
Equipment View of Transfer Job — A transfer job may
involve a number of equipment and ports. Each of the
involved equipment is given a Transfer Job Create
request that specifies only the portion of the overall
transfer job that involves that equipment. Only the host
is guaranteed a complete picture of a compound
transfer. In the example where a transfer job was
created to move a transfer object from “X” to “Y” via
transfer agent “T,”
• “X” would see send material to “T,”
• “Y” would see receive material from “T,” and
• “T” would see get material from “X” and put
material on “Y.”
Atomic Transfer Sequencing Guidelines — When the
transfer job given to an equipment contains multiple
atomic transfers, the guidelines for performing those
transfers are:
• Atomic transfers for a specified port are performed
in the sequence given.
• When a transfer job references multiple ports on
the equipment, these ports may execute their
atomic job sequences in parallel to the other ports.
See Figure 4.1 for an illustration of the flow of a
complex transfer job from the view of one equipment.
The three parallel paths show a possible chronology for
a transfer job.