NJU3423

The NJU3423 has the following features including Display ON/OFF Function;Display Scan Function (Digit Signal);Display Data RAM 22 x 8 Bits;Key Input Data RAM 8 x 4 Bits;Key Scan Function  8 x 4 Key max.;I/O Port (4 Ports);LED Driving Port(4 Ports);CR Oscillation Circuit on-chip (fosc=5.5MHz Typ);External CLK Terminal.

The NJU3423 is a VFD (Vacuum Fluorescent Display) Controller Driverwith key function. NJU3423 contains display data RAM, address counter, command register,high voltage drivers, and serial interface circuit.The display data,the command data and the key scanning data can be transmitted with the serial interface, and VFD driving voltage is up to 45V. The NJU3423  is useful for car audio,VCR and other VFD application items.Reset by RST terminal and Power on reset are operated as same as the instruction reset. The condition of output terminals of NJU3423 and registers are shown in bellow after reset operation.When the first word of the serial data is recognized as the address of the display data RAM( The upper three bits of a byte must be "0".), the lower 5bits are set into the address counter.The display data, which are input sequentially after the address code are set into the addressed area of display data RAM and the address counter is incremented automatically for next data.

The NJU3423 incorporates four I/O ports and four LED driver ports. I/O ports are constructed by the N-channel open-drain type FET with the pull-up resistor. When the output data is set into D3~D0, these I/O ports can be used as the output terminal. In case of input mode "H" level must be set into D3~D0, then these I/O ports can be used as the input terminal with pull-up resistor. The P3~PO data of input or output is transferred to the MPU with Key Input Data (K3~KO), by the serial interface. When the power supply is turned on, the output data is "H". And the data is hold until the next data is transferred.