III PERIPHERAL BLOCK: PRESCALER

Programming Notes

(1)For the prescaler clock, the clock source same as the CPU operating clock must be selected.

(2)In the following cases, the prescaler output clock may contain a hazard:

•If, during outputting of a clock, its division ratio is changed

•When the clock output is switched between on and off

•When the oscillation circuit is turned off or the CPU operating clock is switched over

Before performing these operations, make sure the 16-bit and 8-bit programmable timers and the A/D converter are turned off.

(3)When the 16-bit and 8-bit programmable timers and the A/D converter do not need to be operated, turn off the clock supply to those peripheral circuits. This helps to reduce current consumption.

(4)Be aware that some peripheral circuits stops operating when the prescaler is turned off (PSCON (D5) / Power control register (0x40180) = "0") as well as the peripheral circuits that use the prescaler output clock.

The prescaler status affects the peripheral circuits shown below.

(A)Peripheral circuits that use the clock generated by the prescaler

•16-bit programmable timers (watchdog timer)

•8-bit programmable timers (DRAM refresh, serial interface)

•A/D converter

(B)Peripheral circuits that use the clock supplied to the prescaler (the source clock for prescaler)

•16-bit programmable timers (watchdog timer)

•8-bit programmable timers (DRAM refresh)

•A/D converter

•Serial interface

•Input/output ports

If none of all circuits of the above (A) and (B) need to be used, turn off the prescaler (PSCON = "0"). If a circuit of the above (A) or (B) need to be used, do not turn off the prescaler. When the prescaler is turned off, the clock supply to the circuits of the above (B) stops. When some these circuits of the above (A) need to be used, turn off all other unnecessary circuits and stop the clock supply from the prescaler to those circuits.

B-III-2-8

EPSON

S1C33L03 FUNCTION PART