Numeric LCD Display - Serial, Expandable - Sunrom Technologies

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Pin Configuration PIN# Name Details GND Ground Ground of Power +V + Power 3-5V Power input CLK Clock Serial Clock LAT Latch Latching of data to output DAT Data Serial data input COM LCD Common Common signal of LCD Display Next Display if required DISPLAY DATA FROM MCU Operation The MCU is required to drive the LCD pins with 50% square waves of 20ms time(10ms High, 10ms Low). Each segment on this LCD is connected to the COM backplane and a separate pin. When a pin is driven in phase with the COM pin, the corresponding LCD segment gets zero voltage, and is off. When a pin is driven in reverse of the COM pin, the corresponding segment gets an alternating voltage, and lights up. The 10ms interrupt routine in microcontroller is called periodically to invert all pins of the LCD to generate the 50% square wave. 1 Frame = 20 MiliSecond = 50 Hz refresh rate 10ms COM pin High 10ms COM pin Low Segment is phase with COM pin, will become OFF Segments out of phase with COM pin will become ON Once COM pin is set, a function is called will serially outputs all status of segments. If the segment is in phase to COM pin they become OFF. And Segments which are made out of phase to COM pin becomes on. We provide a detailed commented source code to drive the LCD. See last pages of document. 2 Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com
Register Mapping Each display has four serial addressable 8 bit registers. You can shift in data through clock pulses and make latch pulse to affect the output after all 32 bits(4x8 bits) are clocked in. Register 3,Misc Register2,DISPLAY1 Register1,DISPLAY2 Register0, DISPLAY3 Bit Register3, Misc Register2, Disp# #1 Register1, Disp#2 Register0, Disp#3 7 K segment(for 1) DP1 DP2 DP3 6 X 1E 2E 3E 5 Y 1D 2D 3D 4 ^ 1C 2C 3C 3 ~ 1G 2G 3G 2 LOWBAT 1F 2F 3F 1 COL 1A 2A 3A 0 Not used 1B 2B 3B Cascading multiple display for expansion Can drive multiple displays easily. Cascading multiple display is easy, One side output goes to output of next display. No extra IO from MCU is required. Only software expansion is required, Provision is given in sample code. MCU 3 Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com
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Page 5 and 6: Sample Application - AT89S52 Th sam
Page 7 and 8: void shift_data(unsigned char one_z
Page 9: void test_display_mode() { unsigned

Numeric LCD Display - Serial, Expandable - Sunrom Technologies

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