The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 7 Figure 7-1. You can detect the state of a toggle or slide switch at an input port. switch (A) to one of these inputs, the external pull-up is optional. The pulldown resistor for switch (B) is 1.5K to ensure a valid logic low for LSTTL inputs. With an 8052-BASIC or CMOS input, you can use a 10K pulldown resistor. If you want to offer a choice among several options, a rotary switch can do the job. Figure 7-2 shows an 8-position switch connected to an 8-bit input port. Reading a Switch To find the state of a switch, you read the byte at its address and use BASIC-52’s logical operators to find the value of the bit of interest, just as you did when reading input ports in Chapter 6. For example, to find the logic state of a switch at bit 7 of an input port at E000h, use this statement: A=(XBY(0E000H).AND.80H)/80H Or, in more general terms, use this format: A=(XBY(address).AND.2**bit)/2**bit 110 The Microcontroller Idea Book
Switches and Keypads Figure 7-2. Use a rotary switch to allow users to choose from among several options. where address is the location of the byte to be read in memory and bit is the bit number of the switch. Detecting a Switch Press Momentary switches are useful when you want to get the computer’s attention. For example, you might have a program that normally displays the current temperature and time, but switches to a setup routine when you press a switch. On a normally open pushbutton (momentary) switch, the contacts close when you press the switch, then open as you release it. In a normally closed momentary switch, the contacts open when you press, and close on release. Using Interrupts An easy way to detect a switch press is with an external interrupt. The 8052-BASIC automatically detects the switch press and branches to an interrupt-handling subroutine. The Microcontroller Idea Book 111
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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
Page 69 and 70: Saving Programs Figure 4-5. Additio
Page 71 and 72: problems with EPROMs that have a 10
Page 73 and 74: supply. The chip requires an additi
Page 75 and 76: Programming 5 Programming When you
Page 77 and 78: Subroutines have two advantages. Fi
Page 79 and 80: Programming • Hexadecimal numbers
Page 81 and 82: Programming It can be hard to find
Page 83 and 84: Programming Math Operators = + - *
Page 85 and 86: Programming expression / expression
Page 87 and 88: Programming DO: [program statements
Page 89 and 90: Programming LOG(expression) Returns
Page 91 and 92: Programming PH0.@ Same as PRINT@, b
Page 93 and 94: Programming RCAP2 Retrieves or assi
Page 95 and 96: 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: Switches and Keypads 7 Switches and
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 and 148: Displays Figure 8-7. With the TC721
Page 149 and 150: Displays Figure 8-8. With a charact
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
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different ground symbols for the tw
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10 REM use single-ended mode 20 REM
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Using Sensors to Detect and Measure
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Clocks and Calendars 10 Clocks and
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Listing 10-1. Uses BASIC-52’s rea
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Clocks and Calendars Figure 10-1. P
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Clocks and Calendars Table 10-1. Re
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If you want an alarm frequency othe
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Clocks and Calendars Listing 10-3 (
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Clocks and Calendars Listing 10-3 (
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Control Circuits 11 Control Circuit
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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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