Data Tlb Protection Violation Exception; Initial Page Write Exception - Hitachi SH7751 Hardware Manual

3.6.6

Data TLB Protection Violation Exception

A data TLB protection violation exception occurs when, even though a UTLB entry contains
address translation information matching the virtual address to which a data access is made, the
actual access type is not permitted by the access right specified by the PR bit. The data TLB
protection violation exception processing carried out by hardware and software is shown below.
Hardware Processing: In the event of a data TLB protection violation 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'0A0 in the case of a read, or H'0C0 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 0100 to the contents of VBR, and
starts the data TLB protection violation exception handling routine.
Software Processing (Data TLB Protection Violation Exception Handling Routine): Resolve
the data TLB protection violation, execute the exception handling return instruction (RTE),
terminate the exception handling routine, and return control to the normal flow. The RTE
instruction should be issued at least one instruction after the LDTLB instruction.
3.6.7

Initial Page Write Exception

An initial page write exception occurs when the D bit is 0 even though a UTLB entry contains
address translation information matching the virtual address to which a data access (write) is
made, and the access is permitted. The initial page write exception processing carried out by
hardware and software is shown below.
Hardware Processing: In the event of an initial page write 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.
Rev. 3.0, 04/02, page 79 of 1064