HD6417750 Datasheet, PDF (121/1039 Pages) Renesas Technology Corp – SuperH RISC engine

Here, access to the PCMCIA interface area by accessing an area of P1, P2, or P4 from the CPU is
disabled.
In addition, the PCMCIA interface area is always accessed by the DMAC with the values of
CHCRn.SSAn, CHCRn.DSAn, CHCRn.STC, and CHCRn.DTC in the DMAC. For details, see
section 14, Direct Memory Access Controller (DMAC).
P0, P3, U0 Areas: The P0 area (excluding addresses H'7C00 0000 to H'7FFF FFFF), P3 area, and
U0 area (excluding addresses H'7C00 0000 to H'7FFF FFFF) allow access using the cache and
address translation using the TLB. These areas can be mapped onto any external memory space in
1-, 4-, or 64-kbyte, or 1-Mbyte, page units. When CCR is in the cache-enabled state and the TLB
enable bit (C bit) is 1, accesses can be performed using the cache. In write accesses to the cache,
switching between the copy-back method and the write-through method is indicated by the TLB
write-through bit (WT bit), and is specified in page units.
Only when the P0, P3, and U0 areas are mapped onto external memory space by means of the
TLB, addresses H'1C00 0000 to H'1FFF FFFF of area 7 in external memory space are allocated to
the control register area. This enables on-chip peripheral module control registers to be accessed
from the U0 area in user mode. In this case, the C bit for the corresponding page must be cleared
to 0.
P1, P2, P4 Areas: Address translation using the TLB cannot be performed for the P1, P2, or P4
area (except for the store queue area). Accesses to these areas are the same as for physical memory
space. The store queue area can be mapped onto any external memory space by the MMU.
However, operation in the case of an exception differs from that for normal P0, U0, and P3 spaces.
For details, see section 4.7, Store Queues.
3.3.4 On-Chip RAM Space
In the SH7750 Series, half of the instruction cache can be used as on-chip RAM. This can be done
by changing the CCR settings.
When the operand cache is used as on-chip RAM (CCR.ORA = 1), P0 area addresses H'7C00
0000 to H'7FFF FFFF are an on-chip RAM area. Data accesses (byte/word/longword/quadword)
can be used in this area. This area can only be used in RAM mode.
3.3.5 Address Translation
When the MMU is used, the virtual address space is divided into units called pages, and
translation to physical addresses is carried out in these page units. The address translation table in
external memory contains the physical addresses corresponding to virtual addresses and additional
information such as memory protection codes. Fast address translation is achieved by caching the
contents of the address translation table located in external memory into the TLB. In the SH7750
Series, basically, the ITLB is used for instruction accesses and the UTLB for data accesses. In the
Rev. 6.0, 07/02, page 69 of 986