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Cisco 7200 Series Routers

Field Notice: FN - 28155 - 7200 NSE-1 - Cache Controller Bus Contention Causes Network Services Engine (NSE-1) to Hang - RMA Required


Revised August 10, 2006
April 13, 2004



NOTICE:

THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE FIELD NOTICE OR MATERIALS LINKED FROM THE FIELD NOTICE IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS FIELD NOTICE AT ANY TIME.

Products Affected

Product Top Assembly Printed Circuit Assembly
Part Number Part Number
NSE-1  800-05272-01 through 800-05272-05   73-4068-01 through 73-4068-03
NSE-1 -BUN 800-05272-01 through 800-05272-05 73-4068-01 through 73-4068-03
NSE-1= 800-05272-01 through 800-05272-05 73-4068-01 through 73-4068-03

Problem Description

The network services engine (NSE-1) may hang due to a timing problem with the CPU SysAD bus and the read bypass circuit causing bus contention on the Route Processor (RP) SysAD bus.  

Background

There is a circuit on NSE-1 called the read bypass circuit that allows read cycles to avoid going through the Field-Programmable Gate Array (FPGA). This circuit works by latching the sysad data from the CPU and then, if it is a cycle that can use the read bypass, redrive the latched data to the Network Controller Board (NCB). The basic problem is that the read bypass drives on the very next cycle and this may cause bus contention as the CPU gets off the bus and the read bypass transceivers begin driving the bus.

This issue occurs during normal operations on boards with susceptible parts, such as boards with slower than typical CPUs and faster than typical read bypass transceivers.  

Problem Symptoms

Problem symptoms include the error messages listed below. The failure can also result in a complete hang of the router.

When the NSE-1 hangs, the router will not recover on its own, will not respond to console "break" or to the faceplate push button Non-Maskable Interrupt (NMI).

Examples of error messages encountered during problem manifestation are as follows:

CACHE PARITY EXCEPTION

*** System received a Cache Parity Exception ***
signal= 0x14, code= 0xe0714000, context= 0x60c43580
PC = 0x604a6c0c, Cause = 0x2420, Status Reg = 0x34008002

DATA PARITY EXCEPTION

Error: SysAD, data cache, fields: data, 1st dword
physical addr(21:3) 0x1E432C0,
virtual address is imprecise.

Imprecise Data Parity Error

Imprecise Data Parity Error

Unexpected exception, CPU signal 20, PC = 0x60A7F198

CACHE ERROR EXCEPTION

*** Cache Error Exception ***
CacheErr Reg = 0x84404c50
ErrorEPC Reg = 0xbfc040d8
DErrAddr0 Reg = 0x4cc0
DErrAddr1 Reg = 0x4cb8
PC = 0xbfc040d8, Cause = 0xc000, Status Reg = 0x3040d004

Note: Even though this has been identified as a bus contention issue ensure you have viewed the 7200 Fault Tree document to rule out other potential issues, such as watchdog timeout or a single event upset (SEU or PMPE) that are not part of this Field Notice.  

Workaround/Solution

Cisco recommends a fix-on-fail strategy for this problem. There is no workaround available.

As of approximately June 2004, new products that were manufactured under Engineering Change Order (ECO) E076743 are guaranteed to be free of this problem.

Refer to How to Identify Hardware Levels below for instructions on how to view the version of in-service product.

Service Logistics has known-good inventory at this time.

The standard RMA process and delivery times are in effect.

Refer to the How to Identify Hardware Levels section to confirm that the suspect NSE-1 unit(s) are properly identified as being within the range of product affected with this issue. 

How To Identify Hardware Levels

C7200VXR>sh c7200

< text omitted>

C7200 PE EEPROM:
Hardware Revision : 2.0
Top Assy. Part Number :800-05272-05
Part Number : 73-4068-03
Board Revision : A0
PCB Serial Number : 23271847
RMA History : 00
Fab Version : 04
Fab Part Number : 28-3146-04
Product Number : NSE-1
Board Revision :

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