Hitachi 201
Data cannot be written from the DMAC to cache memory. When the DMAC causes a write to
memory, the contents of memory and the cache contents will be different. To rewrite the contents
of memory, the cache memory must be purged with software if the possibility exists that the data
for that address exists in the cache.
When the CPU starts a read access to a cache area, it first takes a cycle to find the cache. If there is
data in the cache, it fetches it and completes the access. If there is no data in the cache, cache data
is filled via the internal bus, so four consecutive longword reads occur. Misses that occur when
byte or word operands are accessed or branches occur to odd word boundaries (4n + 2 addresses)
are always filled in by longword accesses on the chip-external interface. In the cache-through area,
the access is to the actual access address. When the access is an instruction fetch, the access size is
always longword.
For cache-through areas and on-chip peripheral module read cycles, after an extra cycle is added
to determine the cycle, the read cycle is started through the internal bus. Read data is sent to the
CPU through the cache bus.
When word write cycles access cache area, the cache is searched for. When the data of said
address is found, it is written here. In parallel to this, the actual writing occurs through the internal
bus. When it has the right to use the Internal bus, it notifies the CPU that the write is completed
without waiting for the actual writing to the on-chip peripheral module or off the chip to end.
When it does not have the right to use the internal bus, as when it is being used by the DMAC or
the like, it waits until it gets the bus before notifying the CPU of completion.
Accesses to cache-through areas and on-chip peripheral modules work the same as in the cache
area, except for the cache search and write.
Because the bus state controller has one level of write buffer, the internal bus can be used for
another access even when the chip-external bus cycle has not ended. After a write has been
performed to low-speed memory off the chip, performing a read or write with an on-chip
peripheral module enables an access to the on-chip peripheral module without having to wait for
the completion of the write to low-speed memory.
During reads, the CPU always has to wait for the end of the operation. To immediately continue
processing after checking that the write to the device of actual data has ended, perform a dummy
read access to the same address consecutively to check that the write has ended.
The bus state controller’s write buffer functions the same way during accesses from the DMAC. A
dual-address DMA transfer thus starts up in the next read cycle without waiting for the end of the
write cycle. When both the source address and destination address of the DMA are external spaces
to the chip, however, it must wait until the completion of the previous write cycle before starting
the next read cycle.
Summary of Contents for SH7095
Page 1: ...SH7095 Hardware User Manual ...
Page 23: ...12 Hitachi ...
Page 63: ...52 Hitachi ...
Page 77: ...66 Hitachi ...
Page 105: ...94 Hitachi Figure 5 14 Pipeline Operation when Interrupts are Enabled by Changing the SR ...
Page 127: ...116 Hitachi ...
Page 152: ...Hitachi 141 Figure 7 8 Example of 32 Bit Data Width SRAM Connection ...
Page 157: ...146 Hitachi Figure 7 13 Synchronous DRAM 32 bit Device Connection ...
Page 161: ...150 Hitachi Figure 7 15 Basic Burst Read Timing Auto Precharge ...
Page 167: ...156 Hitachi Figure 7 20 Burst Read Timing Bank Active Same Row Address ...
Page 168: ...Hitachi 157 Figure 7 21 Burst Read Timing Bank Active Different Row Addresses ...
Page 169: ...158 Hitachi Figure 7 22 Write Timing No Precharge ...
Page 170: ...Hitachi 159 Figure 7 23 Write Timing Bank Active Same Row Address ...
Page 180: ...Hitachi 169 Figure 7 29 Example of a DRAM Connection 32 Bit Data Width ...
Page 190: ...Hitachi 179 Figure 7 36 Example of Pseudo SRAM Connection 1 M pseudo SRAM ...
Page 191: ...180 Hitachi Figure 7 37 Example of Pseudo SRAM Connection 4 M pseudo SRAM ...
Page 209: ...198 Hitachi Figure 7 50 Master and Partial Share Master Connections ...
Page 231: ...220 Hitachi ...
Page 287: ...276 Hitachi ...
Page 307: ...296 Hitachi Note For a CPU writing H AA55 to FRC Figure 11 2 FRC Access Operation Write ...
Page 308: ...Hitachi 297 Note For an FRC reading from a CPU H AA55 Figure 11 3 FRC Access Operation Read ...
Page 333: ...322 Hitachi ...
Page 370: ...Hitachi 359 Figure 13 12 Sample Flowchart for Receiving Multiprocessor Serial Data ...
Page 371: ...360 Hitachi Figure 13 12 Sample Flowchart for Receiving Multiprocessor Serial Data cont ...
Page 395: ...384 Hitachi ...
Page 402: ...Hitachi 391 Figure 15 6 PLL Synchronization Settling Timing ...
Page 408: ...Hitachi 397 Figure 15 13 Bus Release Timing Slave Mode With PLL1 Off ...
Page 436: ...Hitachi 425 Figure 15 33 Synchronous DRAM Mode Register Write Cycle TRP 1 Cycle ...
Page 437: ...426 Hitachi Figure 15 34 Synchronous DRAM Mode Register Write Cycle TRP 2 Cycles ...
Page 449: ...438 Hitachi Figure 15 46 DRAM CAS Before RAS Refresh Cycle TRP 1 Cycle TRAS 2 Cycles PLL On ...
Page 454: ...Hitachi 443 Figure 15 51 DRAM CAS Before RAS Refresh Cycle TRP 1 Cycle TRAS 2 Cycles PLL Off ...
Page 461: ...450 Hitachi Figure 15 58 Pseudo SRAM Auto Refresh Cycle PLL On TRP 1 Cycle TRAS 2 Cycles ...
Page 462: ...Hitachi 451 Figure 15 59 Pseudo SRAM Self Refresh Cycle PLL On TRP 1 Cycle TRAS 2 Cycles ...
Page 467: ...456 Hitachi Figure 15 64 Pseudo SRAM Auto Refresh Cycle PLL Off TRP 1 Cycle TRAS 2 Cycles ...
Page 468: ...Hitachi 457 Figure 15 65 Pseudo SRAM Self Refresh Cycle PLL Off TRP 1 Cycle TRAS 2 Cycles ...
Page 471: ...460 Hitachi Figure 15 68 Interrupt Vector Fetch Cycle PLL On No Waits ...
Page 472: ...Hitachi 461 Figure 15 69 Interrupt Vector Fetch Cycle PLL Off No Waits ...
Page 473: ...462 Hitachi Figure 15 70 Interrupt Vector Fetch Cycle 1 External Wait Cycle ...
Page 474: ...Hitachi 463 Figure 15 71 Address Monitor Cycle ...
Page 490: ...Hitachi 479 B 2 Register Chart ...