HD6417750RF240DV Datasheet, PDF (147/1132 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7750 Series

SH7750, SH7750S, SH7750R Group
Section 3 Memory Management Unit (MMU)
3.5.5 Avoiding Synonym Problems
When 1- or 4-Kbyte pages are recorded in TLB entries, a synonym problem may arise. The
problem is that, when a number of virtual addresses are mapped onto a single physical address, the
same physical address data is recorded in a number of cache entries, and it becomes impossible to
guarantee data integrity. This problem does not occur with the instruction TLB or instruction
cache. In the SH-4, entry specification is performed using bits [13:5] of the virtual address in order
to achieve fast operand cache operation. However, bits [13:10] of the virtual address in the case of
a 1-Kbyte page, and bits [13:12] of the virtual address in the case of a 4-Kbyte page, are subject to
address translation. As a result, bits [13:10] of the physical address after translation may differ
from bits [13:10] of the virtual address.
Consequently, the following restrictions apply to the recording of address translation information
in UTLB entries.
1. When address translation information whereby a number of 1-Kbyte page UTLB entries are
translated into the same physical address is recorded in the UTLB, ensure that the VPN [13:10]
values are the same.
2. When address translation information whereby a number of 4-Kbyte page UTLB entries are
translated into the same physical address is recorded in the UTLB, ensure that the VPN [13:12]
values are the same.
3. Do not use 1-Kbyte page UTLB entry physical addresses with UTLB entries of a different
page size.
4. Do not use 4-Kbyte page UTLB entry physical addresses with UTLB entries of a different
page size.
The above restrictions apply only when performing accesses using the cache. When cache index
mode is used, VPN [25] is used for the entry address instead of VPN [13], and therefore the above
restrictions apply to VPN [25].
Note:
When multiple items of address translation information use the same physical memory to
provide for future SuperH RISC engine family expansion, ensure that the VPN [20:10]
values are the same. Also, do not use the same physical address for address translation
information of different page sizes.
R01UH0456EJ0702 Rev. 7.02
Sep 24, 2013
Page 95 of 1076