Section 6 Bus Controller
Rev. 3.00 Jan 25, 2006 page 143 of 872
REJ09B0286-0300
6.9.2
Bus Transfer Timing
When a bus request is received from a bus master with a higher priority than that of the bus master
that has acquired the bus and is currently operating, the bus is not necessarily transferred
immediately. Each bus master can relinquish the bus at the timings given below.
CPU:
The CPU is the lowest-priority bus master, and if a bus request is received from the DTC or
RFU, the bus arbiter transfers the bus to the DTC.
•
DTC bus transfer timing
The bus is transferred at a break between bus cycles. However, if a bus cycle is executed in
discrete operations, as in the case of a longword-size access, the bus is not transferred
between the component operations. For details, refer to section 2.7, Bus States During
Instruction Execution in the H8S/2600 Series, H8S/2000 Series Programming Manual.
If the CPU is in sleep mode, the bus is transferred immediately.
•
RFU bus transfer timing
The bus is transferred at a break between bus cycles. Even in discrete operations, as in the
case of a longword-size access, the bus can be transferred between the component
operations. For details, refer to section 8, RAM-FIFO Unit (RFU).
If the CPU is in sleep mode, the bus is transferred immediately.
DTC:
The DTC sends the bus arbiter a request for the bus when an activation request is generated.
Since the bus master priority of the DTC is lower than the RFU, the bus arbiter transfers the bus
mastership from the DTC to the RFU if the RFU requests the bus.
•
RFU bus transfer timing
The bus is transferred at a break between bus cycles. However, if a bus cycle is executed in
discrete operations, as in the case of a longword-size access, the bus is not transferred between
the component operations. In addition, in 32-bit access by the DTC, the bus is not transferred
at a break between longword access cycles. For details, refer to section 8, RAM-FIFO Unit
(RFU).
RFU:
The RFU has the highest bus master priority. The RFU sends the bus arbiter a request for
the bus when an activation request is generated. The RFU does not release the bus until it
completes its operation. For details, refer to section 8, RAM-FIFO Unit (RFU).
Summary of Contents for H8S/2158
Page 10: ...Rev 3 00 Jan 25 2006 page viii of lii...
Page 36: ...Rev 3 00 Jan 25 2006 page xxxiv of lii B Product Lineup 863 C Package Dimensions 864 Index 865...
Page 47: ...Rev 3 00 Jan 25 2006 page xlv of lii Appendix Figure C 1 Package Dimensions TBP 112A 864...
Page 54: ...Rev 3 00 Jan 25 2006 page lii of lii...
Page 70: ...Section 1 Overview Rev 3 00 Jan 25 2006 page 16 of 872 REJ09B0286 0300...
Page 118: ...Section 3 MCU Operating Modes Rev 3 00 Jan 25 2006 page 64 of 872 REJ09B0286 0300...
Page 126: ...Section 4 Exception Handling Rev 3 00 Jan 25 2006 page 72 of 872 REJ09B0286 0300...
Page 198: ...Section 6 Bus Controller Rev 3 00 Jan 25 2006 page 144 of 872 REJ09B0286 0300...
Page 326: ...Section 10 8 Bit PWM Timer PWM Rev 3 00 Jan 25 2006 page 272 of 872 REJ09B0286 0300...
Page 440: ...Section 15 Watchdog Timer WDT Rev 3 00 Jan 25 2006 page 386 of 872 REJ09B0286 0300...
Page 606: ...Section 17 I 2 C Bus Interface IIC Rev 3 00 Jan 25 2006 page 552 of 872 REJ09B0286 0300...
Page 742: ...Section 19 Multimedia Card Interface MCIF Rev 3 00 Jan 25 2006 page 688 of 872 REJ09B0286 0300...
Page 750: ...Section 21 D A Converter Rev 3 00 Jan 25 2006 page 696 of 872 REJ09B0286 0300...
Page 768: ...Section 22 A D Converter Rev 3 00 Jan 25 2006 page 714 of 872 REJ09B0286 0300...
Page 770: ...Section 23 RAM Rev 3 00 Jan 25 2006 page 716 of 872 REJ09B0286 0300...
Page 824: ...Section 26 Clock Pulse Generator Rev 3 00 Jan 25 2006 page 770 of 872 REJ09B0286 0300...
Page 844: ...Section 27 Power Down Modes Rev 3 00 Jan 25 2006 page 790 of 872 REJ09B0286 0300...
Page 878: ...Section 28 List of Registers Rev 3 00 Jan 25 2006 page 824 of 872 REJ09B0286 0300...
Page 926: ...Index Rev 3 00 Jan 25 2006 page 872 of 872 REJ09B0286 0300...