4250 datasheet(29/59 Pages) RENESAS

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MITSUBISHI MICROCOMPUTERS

4250 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

: Microcomputer starts its operation after 3584 to 3585 machine cycles for the time

required to stabilize the f(XIN) oscillation.

Stabilizing time a

POF instruction

is executed

f(XIN) oscillation

Return input

(RAM back-up

mode)

f(XIN) stop

Reset

(Stabilizing time a )

K03

K02

K01

K00

Instruction clock divided by 4

Instruction clock divided by 512

Rising waveform (“L”

→ “H”)

Falling waveform (“H”

→ “L”)

Key-on wakeup not used

Key-on wakeup used (“L” level recognized)

Key-on wakeup not used

Key-on wakeup used (“L” level recognized)

Prescaler dividing ratio selection bit

Interrupt valid waveform for INT pin/

key-on wakeup valid waveform selection

bit (Note 2)

Ports G1–G3 key-on wakeup control bit

Ports S0–S3 key-on wakeup control bit

Key-on wakeup control register K0

at reset : 00002

at RAM back-up : state retained

R/W

Notes 1: “R” represents read enabled, and “W” represents write enabled.

2: Set a value to the bit 2 of register K0, and execute the SNZ0 instruction to clear the EXF0 flag after executing at least one

instruction. According to the input state of G0/INT pin, the external interrupt request flag (EXF0) may be set when the

interrupt valid waveform is changed.

Table 14 Key-on wakeup control register

Fig. 24 State transition

Power down flag P

POF instruction

Reset input

q Set source

POF instruction is executed

q Clear source

Reset input

Fig. 25 Set source and clear source of the P flag

Fig. 26 Start condition identified example using the SNZP

instruction

Software start

P = “1”

Yes

Warm start

Cold start

(5) Key-on wakeup control register K0

•

Key-on wakeup control register K0

The interrupt valid waveform for INT pin/key-on wakeup

valid waveform selection bit, the ports G1–G3 key-on

wakeup control bit and the ports S0–S3 key-on wakeup

control bit are assigned to the register K0. Set the contents

of this register through register A with the TK0A instruction.

The TAK0 instruction can be used to transfer the contents

of register K0 to register A.

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