Diagnostic Monitoring Interface on Avago SFP Transceiver
The present application note describes Avago’s SFP transceiver implementation of an enhanced digital diagnostic interface, compliant to the “Digital Diagnostic Monitoring Interface for Optical Transceivers” SFF-8472 Multi-Source Agreement (MSA.) The document also outlines the range of application options, both hardware and software, available to the host system for exploiting the digital diagnostic features of the transceiver. The enhanced digital interface allows real-time access to device operating parameters, and includes optional digital features such as soft control and monitoring of SFP I/O signals. In addition, it fully incorporates the functionality needed to implement digital alarms and warnings, as defined by the SFF-8472 MSA. With the digital diagnostic monitoring interface, the user has capability of performing component monitoring, fault isolation and failure prediction functions on their transceiver based applications.
What is Diagnostic Monitoring Interface (DMI)?
As stated in the SFF-8472 MSA, the digital diagnostic monitoring interface (DMI) is an extension of the serial ID interface defined in the GBIC specification, as well as the SFP MSA. Both specifications define a 256-byte memory map in EEPROM that is accessible over a two-wire serial interface at the 8-bit address 1010000X (0xA0). The digital diagnostic monitoring interface makes use of the 8-bit address 1010001X (0xA2), so the originally defined serial ID memory map remains unchanged. The interface is backward compatible with both the GBIC specification and the SFP MSA.
What Can Digital Diagnostic Monitoring Interface Do?
Literally, DDM function can provide component monitoring on transceiver applications in details. However, DDM’s application is not limited to this. The SFF-8472 added DDM interface and outlined that DDM interface is an extension of the serial ID interface defined in GBIC specification, as well as the SFP MSA. DDM interface includes a system of alarm and warning flags which alert the host system when particular operating parameters are outside of a factory set normal operating. Thus, DDM interface can also enable the end user with the capabilities of fault isolation and failure prediction. This part is to illustrate what can be done with DDM.
Overview of applications of DMI
The digital diagnostic monitoring interface gives the host the ability to implement in-situ component monitoring on transceiver applications. Not only can the system user poll the individual parametric read-backs to monitor transceivers, the user can also take advantage of the DMI soft flags, and alarms and warnings to gauge link/transceiver health. Alarm flags signal impending link fault or significant functionality issues. Warning flags are meant to indicate potential compliance violations or non-ideal operating conditions. Soft Flags (bits on address 0xA2, byte 110) offer a mirror of the hard pin state warnings (e.g. TX fault, RX LOS) accessible via the two-wire serial interface.
The uses of the real-time parametric monitoring data can be broken down into the following functional categories with increasing complexity (either at the system software level or transceiver functional level):
- Operating Environment Compliance Verification
The real-time diagnostic parameters can be monitored to alert the system when the transceiver’s specified operating limits are exceeded and compliance (to standard or datasheet) cannot be ensured. See section 3.2 for an example of implementation of alarms and warnings for compliance verification. - Fault Isolation
The diagnostic information can allow the host to pinpoint the location of a link problem and accelerate system servicing and minimize downtime. - Failure Prediction
The diagnostic information can allow the host system to identify potential link problems. Once identified, a “fail over” technique can be used to isolate and replace suspect devices before system uptime is impacted.
Providing parameter monitoring, fault isolation, and failure prediction, fiber optic transceivers with DDM help to ensure that the business can be proactive in preventative maintenance of the network and ensure business continuity. And it would easy to explain why modern transceivers are with DMI and why AFBR-5715PZ can replace AFBR-5710PZ (without DMI). It is irresistible development trend of industry and technology.
Article Source: http://www.sfp-transceiver-modules.com
