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Bus Controller (BC)
8-70
8.15 Bus Arbitration
In this microcontroller, bus arbitration is implemented through the bus authority request signal (BR) and the bus
authority release signal (BG).
If an external device asserts the BR signal, then once the current bus access that is being executed is completed, the
BG signal is asserted and the bus authority is released to the external device. Once the BR signal is negated, this
LSI negates the BG signal in order to re-acquire the bus authority. However, if a refresh request is generated by the
DRAM control circuit within this microcontroller while the bus authority has been released to an external device,
this LSI negates the BG signal and requests the bus authority back form the external device. The external device
then negates the BR signal in response, and the refresh is executed.
Note that bus arbitration is performed in synchronization with SYSCLK.
Fig. 8-15-1 to 3 show the timing for releasing the bus authority to an external device, and Fig. 8-15-4 shows the
timing when a refresh request is generated while the bus authority has been released. An, CSn, RE, WEn, RASn,
and CAS (and, if there is output on other pins related to the BC, those signals as well) are always output by this
microcontroller which has the bus authority (BG = “H”)*
1
, and go to “Hi-Z” (high impedance) when the bus
authority is released (BG = “L”).
Note that the execution of internal I/O space access requests and external memory space access requests by the
CPU while the bus authority is being released are delayed until the bus authority release is completed.
Accesses which can be executed while the bus authority is being released and accesses which are delayed until bus
authority release is completed are listed below.
(1) Accesses which can be executed while the bus authority is being released
- Internal data RAM space accesses by the CPU
- Internal ROM/internal flash memory space accesses by the CPU
(2) Accesses which are delayed until bus authority release is completed
- Internal I/O space accesses by the CPU
- External memory space accesses by the CPU
Note: For details on pins related to the BC and their statuses, refer to Table 8-5-2, “Operating Status of Pins
Concerning BC.”
*1) However, if a bus access is executed immediately before the bus authority is released to an external device, the
An signal, etc., may go to high impedance, even if BG = “H”, depending on the timing of the completion of that
bus access. Specifically, the An and other signals are placed in the high impedance state at the following
timing relative to the timing at which the BG signal is asserted:
When
n
fr = 4: Simultaneously, or 1, 2, or 3 MCLK cycles before
When
n
fr = 2: Simultaneously, or 1 MCLK cycle before
Here,
n
fr = MCLK frequency/SYSCLK frequency
Summary of Contents for MN103001G/F01K
Page 1: ...MICROCOMPUTER MN1030 MN103001G F01K LSI User s Manual Pub No 23101 050E ...
Page 2: ......
Page 4: ......
Page 6: ......
Page 8: ......
Page 9: ...Table of Contents List of Figures and Tables 0 ...
Page 26: ...xviii ...
Page 27: ...1 0 1 General Specifications ...
Page 35: ...2 CPU 2 ...
Page 57: ...3 Extension Instruction Specifications 3 ...
Page 96: ...Extension Instruction Specifications 3 40 ...
Page 97: ...4 Memory Modes 3 4 ...
Page 102: ...Memory Modes 4 6 ...
Page 103: ...5 Operating Mode 5 ...
Page 107: ...6 Clock Generator 6 13 ...
Page 111: ...7 Internal Memory 7 ...
Page 114: ...Internal Memory 7 4 ...
Page 115: ...8 Bus Controller BC 8 ...
Page 189: ...9 Interrupt Controller 9 ...
Page 220: ...Interrupt Controller 9 32 ...
Page 221: ...10 8 bit Timers 9 10 ...
Page 254: ...8 bit Timers 10 34 ...
Page 255: ...11 16 bit Timers 11 ...
Page 292: ...16 bit Timers 11 38 ...
Page 293: ...12 Watchdog Timer 11 12 ...
Page 302: ...Watchdog Timer 12 10 ...
Page 303: ...13 Serial Interface 13 ...
Page 354: ...Serial Interface 13 52 ...
Page 355: ...14 A D Converter 14 ...
Page 367: ...15 I O Ports 15 ...
Page 431: ...16 Internal Flash Memory 16 ...
Page 439: ...17 17 Ordering Mask ROM ...
Page 442: ...Ordering Mask ROM 17 4 ...
Page 443: ...Appendix ...