NEC Network Controller uPD98502 - Manual (Page 159)

CHAPTER 2 V R 4120A
Preliminary User’s Manual S15543EJ1V0UM 159
Figure 2-61. Common Exception Handling (1/2)
(a) Handling Exceptions other than Cold Reset, Soft Reset, NMI, and TLB/XTLB Refill (Hardware)
BD bit ←1
EPC ←PC−4
EXL ←1
Kernel mode is set and interrupts
are disabled.
= 0 (Normal) = 1 (bootstrap)
Check for multiple exceptions
Kernel mode is set and interrupts are
disabled. •
• EntryHi and X/Context registers are set only
when a TLB Refill, TLB Invalid, or TLB
Modified exception occurs. X/Context ←VPN2
Entry Hi ←VPN2, ASID
Set Cause register (ExcCode, CE)
)
To guideline to common exception handler
Start
Yes
EXL = 1?
(SR1)
No
No Yes
Instruction
in branch delay
slot?
BEV
PC ←FFFF FFFF BFC0 0200H +180H
(Unmapped, uncached space)
M16 = 1?
(config20)
PC ←FFFF FFFF 8000 0000H +180H
(Unmapped, cacheable space)
No Instruction
in delay slot?
BD bit ←1
EPC ←PC−4
EPC ←EIM
BD bit ←0
EPC ← PC
EPC ←EIM
No Yes
Yes
BD bit ←0
EPC ←PC
•
BadVAddr is set only when a TLB Refill, TLB
Invalid, or TLB Modified exception occurs
(BadVAddr is not set when a Bus Error exception
occurs). •
Remark The interrupts can be masked by setting the IE or IM bit.
The Watch exception can be set to pending state by setting the EXL bit to 1.