EM73880 datasheet(24/40 Pages) EMC

24 / 40 page

* This specification are subject to be changed without notice.

EM73880

4-BIT MICRO-CONTROLLER FOR LCD PRODUCT

11.30.2001

Preliminary

LCD DRIVER

EM73880 can directly drive the liquid crystal display (LCD) and has 32 segment, 4 common output pins (1/

2 bias, 1/3 bias). There are total 32x4 dots can be display. The V1, V2, V3, VA, VB, VDD and VSS pins are

the LCD bias generator.

CONTROL OF LCD DRIVER

The LCD driver control command register is P27. When LDC is 0, the LCD is disabled, and user could change

Duty in this situation only the COM and SEG pins are VSS. When LDC is 1, the LCD driver enables.

When the CPU is reseted or during the STOP operation mode, the LCD driver is disabled.

Port27

Initial value : 0000

LDC

DUTY

LDC

LCD display control

DUTY

Driving method select

LCD display disable and change Duty 0 0 0

1/4 duty (1/3 bias)

LCD display enable

0 0 1

1/4 duty (1/2 bias)

0 1 0

1/3 duty (1/3 bias)

0 1 1

1/3 duty (1/2 bias)

1 0 0

1/2 duty (1/2 bias)

1 0 1

Static

1 1 *

Reserved

P21 is the control port of watch-dog-timer, and the WDT time up signal is connected to RESET.

Port 21

3210

Initial value :0000

CWC

WDT

CWC

Clear watchdog timer counter

Clear counter then return to 1

Nothing

WDT

Set watch-dog-timer detect time

03 x 213/LXIN = 3 x 213/32K Hz = 0.75 sec

17 x 213/LXIN = 7 x 213/32K Hz = 1.75 sec

PROGRAM EXAMPLE

To enable WDT with 7 x 213/LXIN detection time.

LDIA #0001B

OUTA P21; set WDT detection time and clear WDT counter

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