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or otherwise prevent the slave access cycle from starting, which prevents the slave from producing
a bus release request. The slave accesses these types of memories after the master finishes any
processing necessary when the self-refresh mode is cleared, such as refresh settings.
7.11
Other Topics
7.11.1
Resets
The bus state controller is completely initialized only in a power-on reset. All signals are
immediately negated, regardless of where in the bus cycle the SH7604 is, and the output buffer is
turned off if the bus arbitration mode is slave. Signal negation is simultaneous with turning the
output buffer off. All control registers are initialized. In standby mode, sleep mode, and a manual
reset, no bus state controller control registers are initialized. When a manual reset is performed,
any executing bus cycles are completed, and then the SH7604 waits for an access. When a cache
fill or 16-byte DMAC transfer is executing, the CPU or DMAC that is the bus master ends the
access in a longword unit, since the access request is canceled by the manual reset. This means
that when a manual reset is executed during a cache fill, the cache contents can no longer be
guaranteed. During a manual reset, the RTCNT does not count up, so no refresh request is
generated, and a refresh cycle is not initiated. To preserve the data of the DRAM, synchronous
DRAM or pseudo-SRAM, the pulse width of the manual reset must be shorter than the refresh
interval. Master mode chips accept arbitration requests even when a manual reset signal is
asserted. When a reset is executed only for the chip in master mode while the bus is released, the
BGR
signal is negated to indicate this. If the
BRLS
signal is continuously asserted, the bus release
state is maintained.
7.11.2
Access as Seen from the CPU or DMAC
The SH7604 is internally divided into three buses: cache, internal, and peripheral. The CPU and
cache memory are connected to the cache bus, the DMAC and bus state controller are connected
to the internal bus, and the low-speed peripherals and mode registers are connected to the
peripheral bus. The user break controller is connected to both the cache bus and the internal bus.
The internal bus can be accessed from the cache bus, but not the other way around. The peripheral
bus can be accessed from the internal bus, but not the other way around. This results in the
following.
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 by software if the possibility exists that the data for
that address exists in the cache.