Fujitsu MB91F109, Hardware Manual

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CHAPTER 3 CLOCK GENERATOR AND CONTROLLER
3.10.1 Stop State
This section provides information on transition to and returning from the stop state.
Figure 3.10.1 shows a stop controller block diagram.
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Stop Controller Block Diagram
Figure 3.10-1 Stop Controller Block Diagram
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Transition to Stop State
❍
Transition to the stop state using an instruction
Write "1" to bit 7 of the STCR register to cause a transition to the stop state.
A stop request is issued, and when the CPU no longer uses the internal bus, the clocks are
stopped in the following order:
CPU clock --> internal bus clock --> internal DMA clock --> internal peripheral clock
The oscillation circuit stops when the internal peripheral clock stops.
<Notes>
• Proceed as follows to cause a transition to the stop state using an instruction.
• Before writing to the STCR, set the same value in CCK1/CCK0 and PCK1/PCK0 of the GCR
to match the CPU clock and peripheral clock gear ratios.
• Do not cause a transition to the stop state while the GCR CHC bit is "0" (operating with PLL).
Before causing a transition to the stop state, always set the GCR CHC bit to "1" (divide-by-
two frequency system) to change the clock.
• At least six consecutive NOP instructions must be provided immediately after writing to the
STCR.
STCR
STOP
clear
.or.
Internal bus
Internal interrupt
Internal reset
CPU hold enabled
CPU hold request
Stop state
indication signal
State tr
ansition control circuit
Stop state transition request signal
Stop signal
State decoder
CPU clock
generation
Internal
bus clock
generation
Internal
DMA clock
generation
Internal
peripheral
clock
generation
Clock stop
request signal Clock release
request signal
Inter
nal cloc
k gener
ation circuit
CPU clock
Internal bus clock
Internal DMA clock
External bus clock
Internal peripheral clock