AT&T 3B2/300 Technical Reference Manual page 301

FUNCTIONAL D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - - -
Fault Code Register
The Fault Code Register (FLTCR) records the last fault and operational states in the MMU. The
output of the
/etc/errdump command includes the FLTCR. The format of the FLTCR 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 TRANS LA TED (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
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
3-48 TECHNICAL REFERENCE MANUAL