Mmu Exceptions; Instruction Tlb Multiple Hit Exception; Instruction Tlb Miss Exception - Hitachi SH7751 Hardware Manual

3.6

MMU Exceptions

There are seven MMU exceptions: the instruction TLB multiple hit exception, instruction TLB
miss exception, instruction TLB protection violation exception, data TLB multiple hit exception,
data TLB miss exception, data TLB protection violation exception, and initial page write
exception. Refer to figures 3.10 and 3.11 for the conditions under which each of these exceptions
occurs.
3.6.1

Instruction TLB Multiple Hit Exception

An instruction TLB multiple hit exception occurs when more than one ITLB entry matches the
virtual address to which an instruction access has been made. If multiple hits occur when the
UTLB is searched by hardware in hardware ITLB miss handling, a data TLB multiple hit
exception will result.
When an instruction TLB multiple hit exception occurs a reset is executed, and cache coherency is
not guaranteed.
Hardware Processing: In the event of an instruction TLB multiple hit exception, hardware
carries out the following processing:
1. Sets the virtual address at which the exception occurred in TEA.
2. Sets exception code H'140 in EXPEVT.
3. Branches to the reset handling routine (H'A000 0000).
Software Processing (Reset Routine): The ITLB entries which caused the multiple hit exception
are checked in the reset handling routine. This exception is intended for use in program
debugging, and should not normally be generated.
3.6.2

Instruction TLB Miss Exception

An instruction TLB miss exception occurs when address translation information for the virtual
address to which an instruction access is made is not found in the UTLB entries by the hardware
ITLB miss handling procedure. The instruction TLB miss exception processing carried out by
hardware and software is shown below. This is the same as the processing for a data TLB miss
exception.
Rev. 3.0, 04/02, page 75 of 1064