
II CORE BLOCK: CLG (Clock Generator)
S1C33T01 FUNCTION PART
EPSON
B-II-6-9
Programming Notes
(1)
Immediately after the high-speed (OSC3) oscillation circuit is turned on, a certain period of time is required for
oscillation to stabilize (for a 3.3-V crystal resonator, this time is 10 ms max.). To prevent the device from
operating erratically, do not use the clock until its oscillation has stabilized.
In particular, if the CPU is set in SLEEP mode during operation using the OSC3 clock, the high-speed (OSC3)
oscillation circuit is turned off during in SLEEP mode and starts oscillating again after SLEEP mode is exited.
To prevent the CPU from operating erratically at restart due to an unstable OSC3 clock, set a sufficient
stabilization waiting time in 8-bit programmable timer 1 to turn on the oscillation stabilization waiting function
after SLEEP mode is exited before entering SLEEP mode.
(2)
The oscillation circuit used for the CPU operating clock cannot be turned off.
(3)
The CPU operating clock can only be switched over when both the OSC3 and OSC1 oscillation circuits are on.
Furthermore, when turning off an oscillation circuit that has become unnecessary as a result of the CPU
operating clock switchover, be sure to use separate instructions for switchover and oscillation turnoff. If these
two operations are processed simultaneously using one instruction, the CPU may operate erratically.
(4)
If the high-speed (OSC3) oscillation circuit is turned off, all peripheral circuits operated using the OSC3 clock
will be inactive.
(5)
If the OSC3 clock is unnecessary, use the OSC1 clock to operate the CPU and turn the high-speed (OSC3)
oscillation circuit off. This helps reduce current consumption.
(6)
In the SLEEP state, the oscillation circuit clock stops, and in the HALT2 mode, the clock supply to peripheral
circuits is stopped.
When restarting from this state, interrupt input from a port can be used as a trigger, but functionally, this
interrupt input operates as level input. Therefore, a level input based restart is performed even in the case of set
edge input.
Restart operation is as follows for rising and falling edges.
In case of rising edge interrupt setting: Restarted by high level input.
In case of falling edge interrupt setting: Restarted by low level input.
In normal operation, a restart begins following the elapse of a given time after execution of the SLP instruction,
but when restart by a falling (rising) level (edge) is set, the operation is as follows.
The restart is effected immediately after execution of the SLP instruction.
As ports are already at the low level when the SLP instruction is executed, there is no falling (rising) edge,
and therefore the SLP state is entered only momentarily, and the restart is effected immediately afterwards.
There was a synchronization circuit using a clock signal in the port input circuit, and as the clock is stopped in
the SLEEP state or HALT2 state, the configuration provided for this synchronization circuit to be bypassed
when restarting. Therefore, a restart is effected when the input level from a port is active by level.
Consequently, the system design should assume that a restart by means of port input from the SLEEP state or
HALT2 state is performed by level.