The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 6 Figure 6-6. Connections for adding an 8255 Programmable Peripheral Interface. crystal frequency of an 8085 interfaced to the 8255. Because the signal timings for an 8052 are very different, these ratings don’t apply and you have to look at the timing diagrams to determine what will work. For use with the 8052-BASIC, use a 5-Mhz or faster 8255 if your crystal is 12 Mhz. Slower crystals can use the 3-Mhz or 5-Mhz versions. 102 The Microcontroller Idea Book
Inputs and Outputs An 8255 Interface Figure 6-6 shows an 8255 (U15) accessed at FC00h in the 8052-BASIC system. Many of the pins connect directly to matching signals in the system: D0-D7 connect to the system’s data bus, A0 and A1 connect to the lowest two address lines, and the RD and WR inputs connect to U2’s matching outputs. CS connects to pin 7 of U11 (from Figure 6-2), which selects the chip at addresses from FC00h to FFFFh. U15 actually uses four of these addresses: FC00h through FC03h. U15’s RESET input is controlled by the same RESET signal at pin 9 of the 8052-BASIC. The three new I/O ports are Port A, Port B, and Port C. Address lines A0 and A1 select the port to be accessed, with Port A at FC00h, Port B at FC01h, and Port C at FC02h. The port pins should connect only to voltages in the range -0.5V to +6.5V. According to Intel’s data sheet, the 82C55 has bus-hold circuits that eliminate the need for external pull-ups on its CMOS inputs. The Control Word You configure the 8255 by writing a control word to a control register addressed at FC03h. The control word has two functions: selecting modes of operation, and setting and clearing port bits. When bit 7 of a byte written to the control register is 1, the control word selects modes of operation for each port and determines whether a port is input, output, or bidirectional. Many combinations of modes and I/O are available. When bit 7 of a byte written to the control register is 0, the control word sets and clears individual bits of Port C. The control word is write-only; you can’t read it. Mode Setting Figure 6-7, from Intel’s data sheet, describes the mode-set control word. The ports are divided into two groups. Group A consists of Port A plus bits 4-7 of Port C, and Group B consists of Port B plus bits 0-3 of Port C. This grouping enables Ports A and B to each use half of Port C for handshaking, or control, signals. To set the mode, bit 7 of the control word must be 1. Bit 2 selects mode 0 or 1 for Group B, and bits 5 and 6 select mode 0, 1, or 2 for Group A. Bits 0, 1, 3, and 4 select whether a port is input or output, with each half of Port C selected independently. The simplest mode is Mode 0, Basic Input/Output. The ports behave very much like the inputs and outputs at U12 and U14. Outputs are latched, so they change only when written to. The inputs are not latched, so the present, or current, value of the input is always read. This statement configures all ports as inputs in mode 0: The Microcontroller Idea Book 103
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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.
Page 61 and 62: Saving Programs Figure 4-3. Circuit
Page 63 and 64: Jumper J4 is optional. It enables y
Page 65 and 66: memory on bootup. This is what allo
Page 67 and 68: 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: Inputs and Outputs Pin Symbol Input
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 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).
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Using Sensors to Detect and Measure
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• 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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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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The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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