
7480 Group and 7481 Group User's Manual
1-160
HARDWARE
1.18.3 Oscillation Operations
(1)
Oscillation Operations
The following clocks can be selected as internal clock
φ by the clock division ratio selection bit of
the CPU mode register.
XIN pin input divided by 2 (high-speed mode) when the bit is ‘0’.
XIN pin input divided by 8 (medium-speed mode) when the bit is ‘1’.
Note: The oscillation circuit is held in the high-speed mode after the system is released from reset.
(2)
Oscillation in Stop Mode
When the STP instruction is executed to enter the stop mode, internal clock
φ stops in the HIGH
state, and the oscillation of f(XIN) stops, as well. At this time, timer 1 goes to ‘FF16’, and f(XIN)/8 is
selected as the count source.
CPU returns from stop mode by reset or accepting an external interrupt request (Note 1). In this time,
internal clock
φ is not supplied to the CPU until an underflow occurs in timer 1, though the oscillation
of f(XIN) and internal clock
φ are started. The reason is that oscillator start-up stabilization time is
required when an external resonator is used.
Note: Activate timer 1 and disable the acceptance of a timer 1 interrupt request before the STP
instruction is executed.
Notes 1: For interrupt sources that can be used to return from the stop mode, refer to Table 1.11.2
Interrupt Sources Available for CPU’s Return from Stop/Wait Mode.
For details of the stop mode, refer to Section 1.19.2 Stop Mode.
(3)
Oscillation in Wait Mode
When the WIT instruction is executed to enter the wait mode, only internal clock
φ stops in the HIGH
state.
When the CPU returns from the wait mode by reset or accepting an interrupt request (Note 2), the
supply of internal clock
φ to the CPU is resumed. Since f(XIN) continues oscillation during the wait
mode, instructions can be executed immediately after the CPU returns from the wait mode.
Notes 2: For interrupt sources that can be used to return from the wait mode, refer to Table 1.11.2
Interrupt Sources Available for CPU’s Return from Stop/Wait Mode.
For details of the wait mode, refer to Section 1.19.3 Wait Mode.
1.18 Oscillation Circuit