SED1520 Series

Oscillator Circuit (SED1520*0A Only)

Alow power-consumption CR oscillator for adjusting the oscillation frequency using Rf oscillation resistor only. This circuit generates a display timing signal. Some of SED1520 and SED1522 series models have a built-in oscillator and others use an external clock. This difference must be checked before use.

Connect the Rf oscillation resistor as follows. To sup- press the built-in oscillator circuit and drive the MPU using an external clock, enter the clock having the same phase as the OSC2 of mater chip into OSC2 of the slave chip.

• MPU having a built-in oscillator

VDD

Master chip

Slave chip

 

 

M/S

 

M/S

 

 

(CS)

(CL)

(CS)

(CL)

 

OSC1

OSC2

OSC1

OSC2

 

 

 

VSS

 

 

 

Rf

 

 

 

 

*2

Open

 

 

 

*1

 

 

*1 If the parasitic capacitance of this section increases, the oscillation frequency may shift to the lower frequency. Therefore, the Rf oscillation frequency must be reduced below the specified level.

*2 A CMOS buffer is required if the oscillation circuit is connected to two or more slave MPU chips.

• MPU driven with an external clock

Y driver

 

SED1521FAA

CL2

 

CL

 

 

 

 

 

 

 

 

 

 

SED1520

Series

 

 

Reset Circuit

Detects a rising or falling edge of an RES input and initializes the MPU during power-on.

•Initialization status

1.Display is off.

2.Display start line register is set to line 1.

3.Static drive is turned off.

4.Column address counter is set to address 0.

5.Page address register is set to page 3.

6.1/32 duty (SED1520) or 1/16 duty (SED1522) is selected.

7.Forward ADC is selected (ADC command D0 is

1and ADC status flag is 1).

8.Read-modify-write is turned off.

The input signal level at RES pin is sensed, and an MPU interface mode is selected as shown on Table 1. For the 80-series MPU, the RES input is passed through the inverter and the active high reset signal must be entered. For the 68-series MPU, the active low reset signal must be entered.

As shown for the MPU interface (reference example), the RES pin must be connected to the Reset pin and reset at the same time as the MPU initialization.

If the MPU is not initialized by the use of RES pin during power-on, an unrecoverable MPU failure may occur.

When the Reset command is issued, initialization

EPSON

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