UPD1724X View Datasheet(PDF) - NEC => Renesas Technology

Part Name

Description

Manufacturer

UPD1724X

4-BIT SINGLE-CHIP MICROCONTROLLERS FOR SMALL GENERAL-PURPOSE INFRARED REMOTE CONTROL TRANSMITTERS

NEC => Renesas Technology 

µPD17240, 17241, 17242, 17243, 17244, 17245, 17246

4. CLOCK GENERATOR

4.1 Instruction Execution Time (CPU Clock) Selection

The µPD17246 is equipped with a clock oscillator that supplies clocks to the CPU and peripheral hardware.

Instruction execution time can be changed in two steps (normal mode and high-speed mode) without changing the

oscillation frequency.

To change the instruction execution time, change the mode of SYSCK (RF: address 02H) of the register file by

using the POKE instruction.

Note, that the mode is actually only changed when the instruction next to the POKE instruction has been executed.

When using the high-speed mode, pay attention to the supply voltage. (Refer to 14. ELECTRICAL SPECIFICATIONS.)

After reset, the normal mode is set.

3

2

1

0

Address After reset R/W

0

0

0

SYSCK RF: 02H

0H

R/W

SYSCK

Selects instruction execution time

0

Normal mode 32/fX (8 µs)

1

High-speed mode 16/fX (4 µ s)

Values in parentheses apply to operation when the system clock fX = 4 MHz.

Data Sheet U15002EJ1V0DS

47

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