The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 8 (1) Write the number you want to display to data inputs B0-B3, and bring a digit-select input (D1-D4) high to select the digit to write to. You can use the same XBY statement to do both. For example, to write 7 to digit 2, use this statement: XBY(port address)=27H. (2) With the data still on B0-B3, bring the digit-select input low. The data must remain on B0-B3 for at least 200 nanoseconds after the digit-select input goes low. For step 1’s example, you would write XBY(port address)=07H. Follow the same procedure for each digit, and the TC7211 will continue to drive the appropriate segments on all four digits. To change the value of a digit, repeat steps 1 and 2. Displaying Messages Sometimes a device has to display more complex messages than simple LEDs and 7-segment displays can handle. For example, you might want to display messages like these: Please enter your access code. Select function: Read Program Verify Exit Wind is from the west at 12 mph Total cost = $5.82 With BASIC-52, you can use the host computer’s display, but this is no help if you want to create a stand-alone project that doesn’t require a personal computer. In these situations, a character-based dot-matrix LCD module is a solution. These modules can display messages made up of numbers, characters of the alphabet, and other symbols (for math functions, for example, or even symbols you design yourself). Figure 8-8 illustrates. Devices that use this type of display include laser printers and test equipment. The Controller Chip A special controller chip makes it easier to use LCD modules than you might think. Hitachi’s HD44780 LCD controller is an 80-lead surface-mount chip that takes care of the details of controlling the individual dots, or segments, on the display. For as low as $10, you can find complete modules that contain an LCD panel and small circuit board containing the 138 The Microcontroller Idea Book
Displays Figure 8-8. With a character-based dot-matrix LCD module, you can display messages as well as numbers. controller chip. Applying power, reading, and writing to the module require just 14 connections, or fewer, depending on your configuration. The HD44780 can control displays of up to 80 characters. Learning to program the HD44780 does take some time and experimenting, but the result is a useful and flexible display. Once you’ve had some practice, future projects using the displays are simpler, and you can reuse or adapt portions of your programs in other projects. Many LCD modules use the HD44780 or a compatible controller (the OKI M6222 is an example). If a module uses the same 14-line interface discussed below, chances are it’s compatible with the HD44780. About the Modules The character-based LCD modules are available from many companies, including Philips, Optrex, and Densitron. The surplus market often has good deals. Complete technical information on the controller and displays is available from Hitachi and the display manufacturers, and from some distributors and catalogs. The display of one of these modules contains one or more rows of character positions. Each character position consists of a matrix that is typically five segments, or dots, wide and eight The Microcontroller Idea Book 139
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The Microcontroller Idea Book Circu
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Table of Contents Chapter 1 Microco
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Chapter 11 Control Circuits 185 Swi
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Introduction Introduction This book
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A chapter on assembly-language inte
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Microcontroller Basics 1 Microcontr
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But along with cheap, powerful, and
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makes sense. For simpler designs, a
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Microcontroller Basics Several tech
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Interpreters and compilers are two
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Inside the 8052-BASIC 2 Inside the
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Inside the 8052-BASIC • You can a
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hardware manuals. For programming,
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Inside the 8052-BASIC Figure 2-2 Pi
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Inside the 8052-BASIC Table 2-2. (p
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Inside the 8052-BASIC Code and data
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Powering Up 3 Powering Up This chap
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Powering Up Table 3-1. Parts list f
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Powering Up Figure 3-2. Truth table
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Powering Up Jumper J3 chooses the c
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Powering Up Figure 3-3. This is the
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Powering Up Construction Tips These
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Powering Up Serial Connectors Conne
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You’re now ready to power up the
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Powering Up PRINT XTAL Line Editing
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Powering Up PORT 1 Bit Values: Bit
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Powering Up Listing 3-3. Allows use
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10 CLOCK 1:TIME=0:SEC=0 20 A=0 30 P
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Saving Programs 4 Saving Programs I
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guaranteed for at least ten years.
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Saving Programs Figure 4-3. Circuit
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Jumper J4 is optional. It enables y
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memory on bootup. This is what allo
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This is the recommended algorithm f
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Saving Programs Figure 4-5. Additio
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problems with EPROMs that have a 10
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supply. The chip requires an additi
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Programming 5 Programming When you
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Subroutines have two advantages. Fi
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Programming • Hexadecimal numbers
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Programming It can be hard to find
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Programming Math Operators = + - *
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Programming expression / expression
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Programming DO: [program statements
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Programming LOG(expression) Returns
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Programming PH0.@ Same as PRINT@, b
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Programming RCAP2 Retrieves or assi
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Programming PRINT TAB(2) “hello
Page 97 and 98: Inputs and Outputs 6 Inputs and Out
Page 99 and 100: Unassigned space remains in the mem
Page 101 and 102: U11 is a 74HCT138 3-to-8-line decod
Page 103 and 104: If you wish, you can wire U14’s i
Page 105 and 106: Inputs and Outputs Figure 6-4. Outp
Page 107 and 108: Inputs and Outputs Listing 6-2. Set
Page 109 and 110: The 82C55 also has CMOS-compatible
Page 111 and 112: Inputs and Outputs Pin Symbol Input
Page 113 and 114: Inputs and Outputs An 8255 Interfac
Page 115 and 116: Inputs and Outputs XBY(0FC03h)=9BH
Page 117 and 118: To set or clear a different bit, de
Page 119 and 120: Switches and Keypads 7 Switches and
Page 121 and 122: Switches and Keypads Figure 7-2. Us
Page 123 and 124: exact value depending on the switch
Page 125 and 126: Switches and Keypads Figure 7-4. Tw
Page 127 and 128: Switches and Keypads Figure 7-6. A
Page 129 and 130: Switches and Keypads Custom Keypads
Page 131 and 132: Switches and Keypads • A single c
Page 133 and 134: Switches and Keypads Listing 7-3. T
Page 135 and 136: Displays 8 Displays In addition to
Page 137 and 138: Displays Figure 8-1. LED interfaces
Page 139 and 140: Displays Figure 8-2. Ways to connec
Page 141 and 142: Displays Figure 8-4. Four output po
Page 143 and 144: Displays Figure 8-5. The ICM7218D c
Page 145 and 146: In Figure 8-5’s circuit, an 82(C)
Page 147: Displays Figure 8-7. With the TC721
Page 151 and 152: Table 8-1. LCD modules containing t
Page 153 and 154: Each character in the CG ROM and CG
Page 155 and 156: Displays Interfacing Full control o
Page 157 and 158: Displays Listing 8-4 (page 2 0f 2).
Page 159 and 160: Displays Listing 8-5. Displays key
Page 161 and 162: Displays Listing 8-6 (page 2 of 2).
Page 163 and 164: Using Sensors to Detect and Measure
Page 165 and 166: • What power supplies are availab
Page 171 and 172: different ground symbols for the tw
Page 173 and 174: 10 REM use single-ended mode 20 REM
Page 181 and 182: Clocks and Calendars 10 Clocks and
Page 183 and 184: Listing 10-1. Uses BASIC-52’s rea
Page 185 and 186: Clocks and Calendars Figure 10-1. P
Page 187 and 188: Clocks and Calendars Table 10-1. Re
Page 189 and 190: If you want an alarm frequency othe
Page 191 and 192: Clocks and Calendars Listing 10-3 (
Page 193 and 194: Clocks and Calendars Listing 10-3 (
Page 195 and 196: Control Circuits 11 Control Circuit
Page 197 and 198: the LSTTL part, and wire the desire
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Control Circuits Listing 11-1. Cont
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Control Circuits Listing 11-2. Demo
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Control Circuits disables the outpu
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Wireless Links 12 Wireless Links Wi
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Wireless Links Figure 12-2. This in
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Wireless Links Because there are th
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Wireless Links Figure 12-4. The GP1
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through the LEDs. If you prefer an
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Wireless Links Figure 12-6. Using a
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Wireless Links Figure 12-7. Using a
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Wireless Links IREDs emit energy at
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In the infrared link, the amount of
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Calling Assembly-language Routines
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into memory in the 8052-BASIC syste
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2048h in code memory. This is becau
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Binary value 1100 0101 Hex equivale
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Successful assembly is a good sign,
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statement must match the address in
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• BASIC-52’s ON EX1 instruction
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Running BASIC-52 from External Memo
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14-1 for longer delays between writ
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In Figure 3-1, tie pin 31 of U2 (EA
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Related Products 15 Related Product
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Finally, a compiled BASIC program u
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Related Products Figure 15-3. Blue
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Sources Appendix A Sources This App
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Programming and Interfacing the 805
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Sources Product Vendors The followi
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Sources Electronics 123 17921 Rowla
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Sources Micro Future 40944 Cascado
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Sources Siemens Components 2191 Lau
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Programs for Loading Files Appendix
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Programs for Loading Files Listing
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Number Systems Appendix C Number Sy
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Number Systems This table shows the
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Index Index A ADC, 158 - 169 addres
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Index S sample and hold, 169 SBC, 3
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