1. Spring 2006 1 EE 316 Computer Engineering Junior Lab LCD modules, PROMs, Serial Ports

2. Spring 2006 2 Topics  Liquid Crystal Display Modules  Eraseable Progrmmable ROMs  Serial Ports

3. Spring 2006 3 Liquid Crystal Display (LCD) modules  Majority of the pixel-based alphanumeric LCD module uses the Hitachi HD44780 LCD controller chip.  Makers are: Densitron, Epson, Hewlett Packard, Optrex, or Sharp.  Most have 16, 20, 24, 32, or 40 characters by 1, 2, or 4 lines.  The LCD module we will use has a single line of 20 characters.  Each character is made of 5x7 dot matrix For more info: http://www.doc.ic.ac.uk/~ih/doc/lcd /

4. Spring 2006 4 LCD Display  To use these LCD module, you have follow the timing requirement very precisely. Pay attention to these times Important times http://www.mil.ufl.edu/imdl/handouts/lcd-faq.htm

5. Spring 2006 5 LCD Initialization  Before you use the LCD, you need to initialize the LCD with a very precise sequence of instructions.  Follow the intialization very accurately  Need to generate a sequence of 8-bit instructions with a minimum timing delay between two instructions  each instruction requires multiple steps raise the enable signal ‘E’, apply data or instruction, lower ‘E’, hold data or instruction  You may store these values in a PROM and apply to the LCD with correct times between two instructions.

6. Spring 2006 6 LCD Initialization Contd.  In this example at the end of the initialization the LCD is asked to return cursor to the home postion and clear previous display.  The LCD is then readied for display data (DD) input. The ASCII code for capital “D” is then sent to the LCD module Initialization begins here Initialization ends here LCD is ready for Display data input ASCII 0x44 = D

7. Spring 2006 7 ASCII code

8. Spring 2006 8 PROM  Read only memory  32K x 8 bits or 64K x 8 bits, etc.  Erasable with UV exposure (15-20 mins)  For 32K, 10 address Pins  8 data Pins  Pin named Vpp used for progrmming  Chip enable  Read enable

9. Spring 2006 9 Power-On Reset  In most sequential circuits (i.e., circuits that have FF, latch, or counters, memories), the initial state may not be known after the power is turned on.  Use a RC circuit for the Reset or Clear the FFs. Choose the RC values for correct timing.

10. Spring 2006 10 PC's Serial Ports ● PC's Serial port (RS-232c interface) is also known as the communication (COM)port. ● The serial port transmits a byte of data by sending 8 bits separately. It adds a start bit, a stop bit and if desired, a parity bit. ● COM ports are bi-directional. Serial ports use a special controller chip known as the Universal Asynchronous Receiver/Transmitter (UART), to function correctly. ● Used to connect to Modems, some printers and digital cameras. Ref: http://computer.howstuffworks.com/serial-port.htmhttp://computer.howstuffworks.com/serial-port.htm

11. Spring 2006 11 PC's Serial Port, contd. ● Serial cables can be longer than parallel cables. ● The RS-232c data uses -3 to -12 V to represent a 1 (called Mark) and +3 to +12 to represent a Logical '0' (called Space). ● Serial data must be converted to TTL/CMOS level for digital circuits. http://www.beyondlogic.org/serial/serial1.htm#40

12. Spring 2006 12 PC's Serial Port, contd. ● One can use the RS-232 drivers and recievers to transform the RS-232 level to TTL/CMOS level. http://www.beyondlogic.org/serial/serial1.htm#40

13. Spring 2006 13 UARTs Universal Asynchronous Receiver/Transmitter ➔ To use the serial data in digital applications, we need to convert the TTL/CMOS serial data into parallel data using UARTs. ➔ Popular UARTs: 16550, 16450 & 8250 series ➔ We will use a CMOS based UART: HD- 6402. Read the data sheet carefully before using. ➔ UARTs use a clock with is 16 times the baud rate of the serial port.

14. Spring 2006 14 UART Timing & Control Issues

15. Spring 2006 15 Interfacing a digital system with a PC (another digital system) PC and its UART and level converter MAXIM 233UART

16. Spring 2006 16 References  http://www.doc.ic.ac.uk/~ih/doc/lcd/ http://www.doc.ic.ac.uk/~ih/doc/lcd/  http://www.mil.ufl.edu/imdl/handouts/lcd-faq.htm http://www.mil.ufl.edu/imdl/handouts/lcd-faq.htm  http://computer.howstuffworks.com/serial-port.htm http://computer.howstuffworks.com/serial-port.htm  http://www.beyondlogic.org/serial/serial1.htm#40 http://www.beyondlogic.org/serial/serial1.htm#40