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4250

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

“ Key-on wakeup

When system returns from RAM back-up state by using the

G0/INT pin, select the return edge (rising edge or falling edge)

with the bit 2 of register K0 according to the external state

before going into the RAM back-up state.

When system returns from RAM back-up state by using the

ports G1–G3 and S0–S3, set the port using the key-on wakeup

function selected with register K0 to “H” level before going into

the RAM back-up state.

G0/INT pin and ports G1–G3, S0–S3 share the circuit which is

used to detect the edge and to recognize “L” level.

The G0/INT pin cannot be set to “no key-on wakeup.”

” External clock input waveform

When the external clock is used, open XOUT pin, and input the

clock waveform into XIN pin shown below. (Refer to Figure 30)

•Duty ratio = 50 %.

•“H” level input voltage=VDD (V), “L” level input voltage=VSS (V).

VDD(V)

t/2 (S)

t/2 (S)

VSS(V)

t (S)

Fig. 30 External clock input waveform

• CR oscillation constant

Use the external 30 pF capacitor and enable to change the

frequency by the external resistor.

Test the system sufficiently because the oscillation constant

depends on the ROM type (mask ROM or PROM).

MITSUBISHI MICROCOMPUTERS

4250 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI

ELECTRIC

31

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