AT&T 3B2/300 Technical Reference Manual page 353

FUNCTIONAL D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - - -
Fault Code Register
The Fault Code Register (FLTCR) is loaded whenever a fault occurs during an MMU operation. The
contents are changed to the default state when the CPU writes to it in the peripheral mode. Reading
the FLTCR does not change the contents. The output of the /etc/errdump command includes the
FL TCR. The format of the FL TCR is as follows.
FAULT CODE REGISTER
BITS 31-11 10 -07 06- 05 04 -00
FIELD RESERVED ACCESS REQUESTED ACCESS XLEVEL FAULT TYPE
The FL TCR fields are defined in the following paragraphs.
RESERVED
Bits 31-11 are reserved for future use. If read, zeros are returned.
ACCESS REQUESTED
Bits 10-07 are used to store the type of access the CPU requested when a fault
occurred. The decode of bits 10-07 indicate the following.
BITS 10 - 07 ACCESS TYPE
0000 MOVE TRANSLATED (MT)
0001 SUPPORT PROCESSOR DATA WRITE
0011
SUPPORT PROCESSOR DAT A FETCH
0111
INTERLOCKED READ
1000 ADDRESS FETCH
1001 OPERAND FETCH
1010
WRITE
1100
INSTRUCTION FETCH AFTER DISCONTINUITY
1101
INSTRUCTION PREFETCH
1110
INSTRUCTION FETCH
ACCESS XLEVEL
Bits 06 and 05 are used to store the execution level of the requested access when
the fault occurred. The decode of bits 06 and 05 indicate the following.
BIT 06 BIT 05 DESCRIPTION
0 0 KERNEL LEVEL
0 1
EXECUTIVE LEVEL
1 0 SUPERVISOR LEVEL
1 1
USER LEVEL
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