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<p>Additional announcements by semiconductor producers regarding the boosting of their capital-spending budgets for 2004 should now be viewed as increasingly bad news for the 2005 semiconductor market.</p>

Data is represented in the registers as either signed or unsigned 16-bit integers. Note that single byte values would be stored with the appropriate leading zeros. Real values are stored with an implied decimal point location. For instance, the value 12.3 dBm” would be stored as 1230010 in a field and has an implied formatting of two decimal places.

Fields holding data longer than 16 bits are stored as a sequence of bytes and accessed through the extended addressing register. ASCII strings are terminated with a null. Note that the extended address register allows the host to read beyond a null termination but not beyond the maximum field size. Integers, floats, or structures are stored as a sequence of bytes .

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Under the OIF spec, registers are classified as falling into one of four lockout levels ranging from level 0 (all lockable registers protected) to level 3 (all lockable registers are writeable). The lockout feature provides a degree of protection from altering registers which impact network traffic. Changing the lock level is accomplished by writing the appropriate key to the lock register.

Error Reporting Errors can be generated for transport layer detected error or for application layer errors. Execution errors are asserted by the application layer and occur when the module is unable to execute the requested command. The module defined under the Tunable Laser MSA encodes the XE flag bit (execution error flag) in the response packet. When the host detects an XE flag in the response packet, it can read the NOP (0x00) register to determine the error field condition. Errors conditions include illegal memory or register references, execution failure, value range errors, etc.

Communication errors are asserted by the transport layer and error detection occurs on the module and host sides of the communication interface. The module examines the in-bound packets (host to module) to see if the checksum or the optional 16-bit cyclic redundancy check (CRC-16) is consistent. An inconsistency results in an unprocessed response packet with the CE flag asserted in the out-bound packet. When the host observes the CE flag, the last in-bound packet is resent.

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The host examines the response packets for consistency by checking the checksum and the optional CRC-16 for the out-bound packet (module to host). If either the CRC or checksum is inconsistent, the host may request the module's last response to be retransmitted by reading the Last Response register (0x13).

Pin Assignments OIF's tunable laser specification calls for the development of a 40-pin module. The pin assignments for the module are shown in Figure 4

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The module select* (MS*) line is used to deselect the module when the host desires to communicate with another device on the same bus. The MS* line can also be used to reset the communication interface terminating any transfers that were in progress.

The Sync Object is broadcast periodically by the Sync Producer. This object provides the basic network clock. The time period between Sync messages is defined by the Communication Cycle Period Object, which may be reset via a configuration tool to the application devices during the boot-up process. There can be a time jitter in transmission by the Sync Producer due to some other objects with higher priority identifiers or by one frame being transmitted just before the Sync Object. The Sync Object is mapped to a single CAN frame with the identifier 128.

Emergency Objects are triggered by the occurrence of a device internal fatal error situation. This makes them suitable for interrupt type error alerts. An Emergency Object may be transmitted only once per 'error event'. As long as no new errors occur on a device, no further Emergency Object can be transmitted. Zero or more Emergency Consumers may receive these. The reaction of the Emergency Consumers is application-specific. CANopen defines several Emergency Error Codes to be transmitted in the Emergency Object, which is a single CAN frame with 8 data bytes.

By means of the Time-Stamp Object, a common time frame reference is provided to application devices. It contains a value of the type Time-of-Day. This object transmission follows the producer/consumer push model. The associated CAN frame has the pre-defined identifier 256 and a 6-byte data field.

CAN is a communication object (COB) oriented network, for which each COB has one or more associated identifiers, which implicitly specify its priority. Thus the allocation of identifiers to the COBs is an essential issue in the system design. In order to reduce configuration effort for simple CANopen networks, a mandatory default-identifier allocation scheme is defined. These identifiers are available in the Pre-operational status and may be modified by means of dynamic distribution. A CANopen device has to provide the corresponding identifiers only for the supported communication objects. The profile ID-allocation scheme consists of a functional part, which determines the object priority and a node-ID-part, which allows distinguishing between devices with the same functionality. The ID-allocation scheme corresponds to a pre-defined master/slave connection set and allows peer-to-peer communication between a single-master device and up to 127 slave devices. It also supports the broadcasting of unconfirmed NMT, Sync, and Time-Stamp Objects. The pre-defined master/slave connection set supports one Emergency Object, one SDO as well as up to four Receive-PDOs and up to four Transmit-PDOs, and the Error Control Object for each slave device. In order to optimize the identifier allocation, the system designer may configure the allocation of identifiers to communication objects.

Standardized profiles (device, interface, and application profiles) developed by CiA members simplify the system designer's job of integrating a CANopen network system. Off-the-shelf devices, tools, and protocol stacks are widely available at reasonable prices. For system designers, it is very important to reuse application software. This requires not only communication compatibility but also interoperability of devices. CANopen is flexible and open enough to enable manufacturer-specific functionality in devices, which can be added to the generic functionality described in the profiles.

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The irony is that in these economic doldrums, innovation may not be competitive in the survival of the fittest” equation. The fittest will be the established-that is to say, mainstream-institutions, while innovation declines because of the inability of innovative companies to reach critical mass before the economy recovers. If this happens, we may delay or even skip a technology generation.

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