192 Hitachi
There are three modes for bus arbitration: master mode, partial-share master mode, and slave
mode. Master mode keeps the bus under normal conditions and permits other devices to use the
bus by releasing it when they request its use. The slave mode normally does not have the bus. It
requests the bus when an external bus access cycle comes up and then releases the bus when the
access is completed. The partial-share master mode only shares CS2 space with external devices .
For the CS2 space, it is in slave mode; for other spaces, it always keeps the bus without any bus
arbitration. The CS space onto which the chip in master mode the chip in partial-share master
mode CS2 space is allocated is determined by the externally connected circuits.
Master or slave mode can be specified using external mode pins. Partial-share master mode is
reached from master mode by setting software. See Section 3, Oscillator Circuits and Operating
Mode, for the external mode pin setting. When a device in master or slave mode does not have the
bus, its bus goes to high impedance, so master mode chips and slave mode chips can be connected
directly. In the partial-share master mode, the bus is always driven, so an external buffer is needed
to connect to a master bus. In master mode, a connection to an external device requesting the bus
can be substituted for the slave mode connection. In the following explanation, external devices
requesting the bus are also called slaves.
The SH7095 has two internal bus masters, the CPU and the DMAC. When an synchronous
DRAM, DRAM or pseudo SRAM is connected and refresh control being performed, the refresh
request becomes a third master. In addition to these, there are also bus requests from external
devices while in the master mode. The priority for bus requests when they occur simultaneously is,
highest to lowest, refresh requests, bus requests from external devices, DMAC and CPU.
When the bus is being passed between slave and master, all bus control signals are negated before
the bus is released to prevent the connected devices from operating in error. Once the bus is
received, the bus control signals change from negated to bus driven. The master and slave passing
the bus between them drive the same signal values, so output buffer conflict is avoided. Turning
the output buffer off for the bus control signals on the side that releases the bus and on at the side
getting the bus can eliminate the high impedance period of the signals. It is usually not necessary
to insert a pull-up resistance into these control signals to prevent malfunction caused by external
noise while they are at high impedance.
Bus permission is performed at the end of the bus cycle. When the bus is requested, the bus is
released immediately if there is no ongoing bus cycle. If there is a current bus cycle, the bus is not
released until the bus cycle ends. Even when there does not appear to be an ongoing bus cycle
when seen from outside the SH7095, it cannot be determined whether or not the bus will be
released immediately when a bus control signal such as a CSn signal is seen, since an internal bus
cycle, such as inserting a wait between access cycles, may have been started. The bus cannot be
released during burst transfers for cache fills or 16-byte DMAC block transfers. Likewise, the bus
cannot be released between the read and write cycles of a TAS instruction. Arbitration is also not
performed between multiple bus cycles produced by a data width smaller than the access size,
such as a longword access to an 8-bit data width memory. Bus arbitration is performed between
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 ...