21264/EV68A Hardware Reference Manual
Privileged Architecture Library Code 6–13
PALcode Entry Points
EachCALL_PAL instruction includes a functionfield that is used to calculate the PC of
itsa ssociatedPALcode entry point. The PALcode OPCDEC exceptionflow will be
invoked ifthe CALL_PAL function field satisfiesany of the following requirements:
Is inthe range of 4016 to 7F16 inclusive
Is greaterthan BF16
Is between0016 an d 3F16 inclusive,and IER_CM[CM] is not equal to the kernel
mode value 0
If noneof the conditions above are met, the PALcodeentry point PC is as follows:
PC[63:15]= PAL_BASE[63:15]
PC[14] = 0
PC[13] = 1
PC[12]= CALL_PAL function field [7]
PC[11:6]= CALL_PAL function field [5:0]
PC[5:1] = 0
PC[0]= 1(PALmode)
6.8.2 PALcode Exception Entry Points
When hardwareencounters an exception, Ibox execution jumps to a PALcodeentry
pointat a P Cde terminedby the type of exception. The return PC of the instruction that
triggeredthe exception is placed in the EXC_ADDR register and onto the return predic-
tionstack.
Table6–8 shows the PALcode exception entry locations and their offsetfrom the
PAL_BASEIPR.
Table 6–8 PALcode Exc eptionE ntryL ocations
EntryName Type Offset16 Description
DTBM_DOUBLE_3 Fault 100 DstreamTB miss on virtual page table entry fetch. Use three-
levelflow.
DTBM_DOUBLE_4 Fault 180 DstreamTB miss on virtual page table entry fetch. Use four-
levelflow.
FEN Fault 200 Floatingpoint disabled.
UNALIGN Fault 280 UnalignedDstream reference.
DTBM_SINGLE Fault 300 DstreamTB miss.
DFAULT Fault 380 Dstr eam fault or virtua l address sign check e rror.
OPCDEC Fault 400 Illegalopcode or function field:
•Opcode 1, 2, 3, 4, 5, 6 or 7
•Opcode 1916 ,1B
16,1D
16,1E
16or 1 F16 ,not PALmode or
not I_CTL[HWE]
•E xtendedprecision IEEE format
•Unimplemented function field of opcodes 1416 or 1C16
IACV Fault 480 Istreamaccess violation or virtual address sign check error.