NEC Network Controller uPD98502 - Manual (Page 161)

CHAPTER 2 V R 4120A
Preliminary User’s Manual S15543EJ1V0UM 161
Figure 2-62. TLB/XTLB Refill Exception Handling (1/2)
(a) Handling TLB/XTLB Refill Exceptions (Hardware)
BD bit ←0 BD bit ←1
EPC ←PC−4
EXL ←1
EPC ←PC
Kernel mode is set and interrupts are disabled.
= 1 (bootstrap) = 0 (Normal)
Check for multiple exceptions
EntryHi ←VPN2, ASID
X/Context ←VPN2
Set Cause register (ExcCode, CE)
To guideline to TLB/XTLB exception handler
Start
Yes
EXL = 1?
(SR1)
No
No Yes
Instruction
in branch delay
slot?
BEV
PC ←FFFF FFFF 8000 0000H + vector offset
(Unmapped, cacheable space)
PC ←FFFF FFFF BFC0 0200H + vector offset
(Unmapped, uncached space)
XTLB Refill
Vector offset = 080H
TLB Refill
Vector offset = 000H
TLB Refill
Vector offset = 180H
No Yes XTLB
Exception?
M16 = 1?
(config20)
No
Instruction
in delay slot?
BD bit ←1
EPC ←PC-4
EPC ←EIM
BD bit ←0
EPC ←PC
EPC ←EIM
No Yes Yes