III PERIPHERAL BLOCK:
Controlling Oscillation
The
The oscillation circuit is turned off by writing "0" to SOSC1 and turned back on again by writing "1". SOSC1 is set to "1" at initial reset, so the oscillation circuit is turned on.
Notes: • When the
•Immediately after the oscillation circuit is turned on, a certain period of time is required for oscillation to stabilize (3 sec max.). To prevent the device from operating erratically, do not use the clock until its oscillation has stabilized.
The
Switching Over the CPU Operating Clock
After an initial reset, the CPU starts operating using the OSC3 clock.
In cases in which some peripheral circuits (e.g., programmable timer, serial interface, A/D converter, and ports) do not need to be operate or processing in
Procedure for switching over from the OSC3 clock to the OSC1 clock
1.Turn on the
2.Wait until the OSC1 oscillation stabilizes (three seconds or more).
3.Change the CPU operating clock (by writing "0" to CLKCHG).
4.Turn off the
∗ Steps 1 and 2 are required only when the
Notes: • Use separate instructions to switch from OSC3 to OSC1 and turn the OSC3 oscillation off. If these operations are processed simultaneously using one instruction, the CPU may operate erratically.
•Make sure the operation of the peripheral circuits, such as the programmable timer and serial interface is terminated before the OSC3 oscillation is turned off in order to prevent them from operating erratically or the prescaler clock is set as OSC1. In addition, in order to prevent incorrect operation, a setup of prescaler must be performed before changing the CPU clock.
Procedure for switching over from the OSC1 clock to the OSC3 clock
1.Turn on the
2.Wait until the OSC3 oscillation stabilizes (10 ms or more for a
3.Switch over the CPU operating clock (by writing "1" to CLKCHG).
Note: The operating clock switchover by CLKCHG is effective only when both oscillation circuits are on and the
OSC1
S1C33L03 FUNCTION PART | EPSON |