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Section 12 Bus State Controller (BSC)
Rev. 4.00 Sep. 14, 2005 Page 401 of 982
REJ09B0023-0400
12.5.13 Others
Reset: The bus state controller (BSC) can be initialized completely only at power-on reset. When
a power-on reset occurs, internal clocks are synchronized by the reset, then all signals are negated
and output buffers are turned off regardless of the bus cycle state. All control registers are
initialized.
In standby, sleep, and manual reset, control registers of the bus state controller are not initialized.
At manual reset, the current bus cycle being executed is completed and then the access wait state
is entered. If a 16-byte transfer is performed by a cache or if another LSI on-chip bus master
module is executed when a manual reset occurs, the current access is cancelled in longword units
because the access request is cancelled by the bus master at manual reset. If a manual reset is
requested during cache fill operations, the contents of the cache cannot be guaranteed. Since the
RTCNT continues counting up during manual reset signal assertion, a refresh request occurs to
initiate the refresh cycle. However, a bus arbitration request by the
BREQ
signal cannot be
accepted during manual reset signal assertion.
Some flash memories may specify a minimum time from reset release to the first access. To
ensure this minimum time, the bus state controller supports a 7-bit counter (RWTCNT). At power-
on reset, the RWTCNT is cleared to 0. After power-on reset, RWTCNT is counted up
synchronously together with CKIO and an external access will not be generated until RWTCNT is
counted up to H'007F. At manual reset, RWTCNT is not cleared.
Access from the Site of the LSI Internal Bus Master: There are three types of LSI internal
buses: a cache bus, internal bus, and peripheral bus. The CPU and cache memory are connected to
the cache bus. Internal bus masters other than the CPU and bus state controller are connected to
the internal bus. Low-speed peripheral modules are connected to the peripheral bus. Internal
memories other than the cache memory are connected bidirectionally to the cache bus and internal
bus. Access from the cache bus to the internal bus is enabled but access from the internal bus to
the cache bus is disabled. This gives rise to the following problems.
On-chip bus masters such as DMAC other than the CPU can access internal memory other than
the cache memory but cannot access the cache memory. If an on-chip bus master other than the
CPU writes data to an external memory other than the cache, the contents of the external memory
may differ from that of the cache memory. To prevent this problem, if the external memory whose
contents is cached is written by an on-chip bus master other than the CPU, the corresponding
cache memory should be purged by software.
Содержание HD6417641
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Страница 228: ...Section 6 Power Down Modes Rev 4 00 Sep 14 2005 Page 178 of 982 REJ09B0023 0400...
Страница 246: ...Section 8 X Y Memory Rev 4 00 Sep 14 2005 Page 196 of 982 REJ09B0023 0400...
Страница 318: ...Section 11 User Break Controller UBC Rev 4 00 Sep 14 2005 Page 268 of 982 REJ09B0023 0400...
Страница 454: ...Section 12 Bus State Controller BSC Rev 4 00 Sep 14 2005 Page 404 of 982 REJ09B0023 0400...
Страница 500: ...Section 13 Direct Memory Access Controller DMAC Rev 4 00 Sep 14 2005 Page 450 of 982 REJ09B0023 0400...
Страница 504: ...Section 14 U Memory Rev 4 00 Sep 14 2005 Page 454 of 982 REJ09B0023 0400...
Страница 566: ...Section 17 Compare Match Timer CMT Rev 4 00 Sep 14 2005 Page 516 of 982 REJ09B0023 0400...
Страница 734: ...Section 18 Multi Function Timer Pulse Unit MTU Rev 4 00 Sep 14 2005 Page 684 of 982 REJ09B0023 0400...
Страница 868: ...Section 21 A D Converter Rev 4 00 Sep 14 2005 Page 818 of 982 REJ09B0023 0400...
Страница 914: ...Section 23 I O Ports Rev 4 00 Sep 14 2005 Page 864 of 982 REJ09B0023 0400...
Страница 956: ...Section 24 List of Registers Rev 4 00 Sep 14 2005 Page 906 of 982 REJ09B0023 0400...
Страница 1016: ...Section 25 Electrical Characteristics Rev 4 00 Sep 14 2005 Page 966 of 982 REJ09B0023 0400...
Страница 1024: ...Appendix Rev 4 00 Sep 14 2005 Page 974 of 982 REJ09B0023 0400...
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