First Failing Register (FFR) - 1.0 English

First Failing Register (FFR) - 1.0 English - PG268

MicroBlaze Triple Modular Redundancy (TMR) Subsystem LogiCORE IP Product Guide (PG268)

Document ID

PG268

Release Date

2025-12-09

Version

1.0 English

The first failing register contains the TMR subsystem fault status. This is a read/write register. Issuing a write request to the first failing register with any data clears bit 3-0 of the register, provided that the MAGIC1 field in the Control Register is correctly set. The register bit assignment is shown in the following table and described in Table 2.

In lockstep mode (C_TMR = 0) bits 19-17 and 3-0 are read-only zero.

Table 1. First Failing Register (FFR)
Reserved		WE	FAT UE	FAT V	FAT 23	FAT 13	FAT 12	Reserved		REC	LM 23	LM 13	LM 12
31	22	21	20	19	18	17	16	15	4	3	2	1	0

Table 2. First Failing Register Bit Definitions
Bits	Name	Access	Reset Value	Description
31-22	Reserved	N/A	0	Reserved
21	Watchdog Expired	R/W	0	Indicates if the watchdog has expired: 0 - The watchdog has not expired. 1 - The watchdog has expired.
20	Fatal Uncorrectable Error	R/W	0	Fatal ECC uncorrectable error has occurred: 0 = No fatal error. 1 = A fatal error has occurred.
19	Fatal Voter Error	R/W	0	Fatal voter error has occurred: 0 = No fatal error. 1 = A fatal error has occurred.
18	Fatal 2-3	R/W	0	Fatal error has occurred for processors 2 and 3 causing transition to Fatal state: 0 = No fatal error. 1 = A fatal error has occurred.
17	Fatal 1-3	R/W	0	Fatal error has occurred for processors 1 and 3 causing transition to Fatal state: 0 = No fatal error. 1 = A fatal error has occurred.
16	Fatal 1-2	R/W	0	Fatal error has occurred for processors 1 and 2 causing transition to Fatal state: 0 = No fatal error. 1 = A fatal error has occurred.
15-4	Reserved	N/A	0	Reserved
3	Recovery	R/W	0	Indicates if a recovery has been performed: 0 = No recovery. 1 = A recovery has occurred.
2⁽¹⁾	Lockstep mismatch 2-3	R/W	0	Lockstep mismatch between processor 2 and 3 causing transition to Lockstep state: 0 = No lockstep mismatch. 1 = Lockstep mismatch has occurred.
1⁽¹⁾	Lockstep mismatch 1-3	R/W	0	Lockstep mismatch between processor 1 and 3 causing transition to Lockstep state: 0 = No lockstep mismatch. 1 = Lockstep mismatch has occurred.
0⁽¹⁾	Lockstep mismatch 1-2	R/W	0	Lockstep mismatch between processor 1 and 2 causing transition to Lockstep state: 0 = No lockstep mismatch. 1 = Lockstep mismatch has occurred.
The Lockstep mismatch bits indicate which processors have detected a mismatch, and if one processor is faulty the two others detect a mismatch. Consequently, two of the three bits is set when one processor can be identified as faulty. For example, if processor 1 is faulty, both processors 2 and 3 detects a mismatch, and the bits have the binary value 011. In case only one or all three of the bits are set, the processors do not agree on which one is faulty, and recovery is not possible.