Data Tlb Multiple Hit Exception; Data Tlb Miss Exception - Hitachi SH7750 Hardware Manual

3.6.4

Data TLB Multiple Hit Exception

A data TLB multiple hit exception occurs when more than one UTLB entry matches the virtual
address to which a data access has been made. A data TLB multiple hit exception is also generated
if multiple hits occur when the UTLB is searched in hardware ITLB miss handling.
When a data TLB multiple hit exception occurs a reset is executed, and cache coherency is not
guaranteed. The contents of PPN in the UTLB prior to the exception may also be corrupted.
Hardware Processing: In the event of a data 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 UTLB 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.
3.6.5

Data TLB Miss Exception

A data TLB miss exception occurs when address translation information for the virtual address to
which a data access is made is not found in the UTLB entries. The data TLB miss exception
processing carried out by hardware and software is shown below.
Hardware Processing: In the event of a data TLB miss exception, hardware carries out the
following processing:
1. Sets the VPN of the virtual address at which the exception occurred in PTEH.
2. Sets the virtual address at which the exception occurred in TEA.
3. Sets exception code H'040 in the case of a read, or H'060 in the case of a write, in EXPEVT
(OCBP, OCBWB: read; OCBI, MOVCA.L: write).
4. Sets the PC value indicating the address of the instruction at which the exception occurred in
SPC. If the exception occurred at a delay slot, sets the PC value indicating the address of the
delayed branch instruction in SPC.
5. Sets the SR contents at the time of the exception in SSR. The R15 contents at this time are
saved in SGR.
6. Sets the MD bit in SR to 1, and switches to privileged mode.
7. Sets the BL bit in SR to 1, and masks subsequent exception requests.
8. Sets the RB bit in SR to 1.
9. Branches to the address obtained by adding offset H'0000 0400 to the contents of VBR, and
starts the data TLB miss exception handling routine.
Rev. 6.0, 07/02, page 84 of 986