Summary Of Data Bus Errors; Additional Status; Data Bus Error Summary - DEC AlphaServer 8200 Technical Manual

System fatal data bus errors are cumulative. Should a second system fatal
error occur, TLSB_FAULT is asserted a second time. If a fatal error is of a
different type than the first, an additional error is set in the TLBER regis-
ter.
2.4.4.8

Summary of Data Bus Errors

Table 2-12 shows all the data bus errors, which nodes are responsible for
detecting the errors, and what error signals are asserted.
Table 2-12 Data Bus Error Summary
Error Description
Uncorrectable Data Error
UDE
CWDE Correctable Write Data Error
Correctable Read Data Error
CRDE
Fatal Data Transmit Check Error
FDTCE
Data Control Transmit Check Error
DCTCE
Sequence Error
SEQE
Data Status Error
DSE
Data Timeout
DTO

2.4.5 Additional Status

In addition to the error bits in the TLBER and TLESRn registers, addi-
tional status is preserved on detection of errors.
These registers can only hold information relative to one error. It is, there-
fore, the responsibility of software to read and clear all error bits and
status. Even when errors occur infrequently there is a chance that a sec-
ond error can occur before software clears all status from a previous error.
The error register descriptions specify the behavior of a node when multi-
ple errors occur.
2-42 TLSB Bus
• The TLESRn registers record an error syndrome (SYNDn) and
whether the node transmitted the data that was read with errors
(TDE).
• The TLBER register records which TLESRn registers contain error
status corresponding to a specific error occurrence (DSn).
• The TLBER register records which nodes detected errors on commands
issued by that node (ATDE).
• The TLBER register records which node transmitted the data that re-
sulted in assertion of TLSB_DATA_ERROR (DTDE). Software must
poll all nodes to find it.
• The TLFADRn registers record the address, command, and bank num-
ber from the command. Software must poll all nodes to find the re-
corded data.
Who Detects Signal
All participants TLSB_DATA_ERROR
All participants TLSB_DATA_ERROR
All participants TLSB_DATA_ERROR
Transmitter TLSB_FAULT
All participants TLSB_FAULT
All nodes TLSB_FAULT
All participants TLSB_FAULT
Commander TLSB_FAULT