20.7 System Clock Output Disabling Function
Output of the system clock (ø) can be controlled by the PSTOP bit in MSTCR. When the PSTOP
bit is set to 1, output of the system clock halts and the ø pin is placed in the high-impedance state.
Figure 20-3 shows the timing of the stopping and starting of system clock output. When the
PSTOP bit is cleared to 0, output of the system clock is enabled. Table 20-4 indicates the state of
the ø pin in various operating states.
Figure 20-3 Starting and Stopping of System Clock Output
Table 20-4 ø Pin State in Various Operating States
Operating State
PSTOP = 0
PSTOP = 1
Hardware standby
High impedance
High impedance
Software standby
Always high
High impedance
Sleep mode
System clock output
High impedance
Normal operation
System clock output
High impedance
T1
T2
(PSTOP = 1)
T3
T1
T2
(PSTOP = 0)
MSTCR write cycle
MSTCR write cycle
High impedance
ø pin
T3
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