The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 4 Figure 4-1. Pinouts for Dallas Semiconductor’s 8K NVRAM and SmartSocket. space (even though it may contain NVRAM, EEPROM, or EPROM), and call the memory beginning at 0, up to 7FFFh or the top of RAM, the RAM space. BASIC-52’s programming commands are designed to meet the requirements for EPROMs, using either of two programming algorithms, or procedures. You can use the same commands to store programs in NVRAM or EEPROM. Like EPROMs, these devices provide nonvolatile storage—in other words, their contents don’t disappear when power is removed. Plus, they have two advantages over EPROMs: they don’t need any special programming voltages, and they don’t need ultraviolet exposure to erase. This makes them much more convenient to use. For these reasons, the first circuit we’ll look at offers a choice of NVRAM or EEPROM for nonvolatile storage. Later, we’ll add circuits that allow you to program EPROMs, for those who want this option. NVRAM Dallas Semiconductor offers NVRAM chips that you can use for nonvolatile storage. These work exactly like static RAM, except that they contain a lithium cell and backup circuits that retain the RAM’s contents when the main power supply is removed. The backup is 48 The Microcontroller Idea Book
guaranteed for at least ten years. Dallas also makes a product called the SmartSocket, which consists of an IC socket with an embedded lithium cell and backup circuits. To create a NVRAM, you plug your own static RAM chip into the SmartSocket. Eight kilobytes is a convenient size that will store many short BASIC-52 programs, or fewer longer ones. For an 8K NVRAM, you can use a DS1225 NVRAM, or a DS1213B or DS1213C SmartSocket with a 6264 or similar static RAM. Figure 4-1 shows the pinouts. The 1213B and 1213C SmartSockets differ only in that the 1213B will also accept a 24-pin 2K SRAM, with pins 1, 2, 27, and 28 unused, and the 1213C will also accept a 32K SRAM, which has address inputs at pins 1 and 26. The DS1225 offers a choice of two write-protect voltages. On the -AB version, write protection is guaranteed when the power supply is less than 4.5V, and write operations are allowed when the power supply is greater than 4.75V. The SmartSockets use these same voltages. On the -AD and -Y versions of the DS1225, write protection is guaranteed when the supply is less than 4.25V, and write operations are allowed when the supply is greater than 4.5V. Either type should work in a BASIC-52 system with a regulated +5V supply. Access times of 250 nanoseconds or less are fine for the NVRAM. Don’t be confused by the fact that Dallas describes its devices by the number of bits they store, rather than the number of bytes. For example, they call the 8-kilobyte DS1225 a 64K device. You can order NVRAMs directly from Dallas Semiconductor (no minimum order), and from other vendors. EEPROM Saving Programs The other option for program storage is EEPROM. A typical EEPROM is guaranteed for 10,000 to 100,000 write cycles, compared to infinite write cycles for NVRAM. Access times for reading an EEPROM are similar to those for static RAM, but writing to EEPROM takes much longer. Most require 2 to 10 milliseconds after a write operation before you can access the chip again. In spite of the drawbacks, I’ve included EEPROM as an option because an 8K EEPROM may cost less than a comparable NVRAM. A typical part number for an 8K EEPROM is 2864 or 28C64. Figure 4-2 shows the pinout for a 28(C)64 EEPROM. Notice that its pinout, too, is very similar to that of a 6264 static RAM. EEPROMs have two common ways of indicating that they are busy performing a write operation and are unable to be accessed. In one type, when the EPROM is busy, the data pins hold the last-written data, but with one or more bits inverted. BASIC-52’s programming The Microcontroller Idea Book 49
Page 1 and 2:
The Microcontroller Idea Book Circu
Page 3 and 4:
Table of Contents Chapter 1 Microco
Page 5 and 6:
Chapter 11 Control Circuits 185 Swi
Page 7 and 8: Introduction Introduction This book
Page 9 and 10: A chapter on assembly-language inte
Page 11 and 12: Microcontroller Basics 1 Microcontr
Page 13 and 14: But along with cheap, powerful, and
Page 15 and 16: makes sense. For simpler designs, a
Page 17 and 18: Microcontroller Basics Several tech
Page 19 and 20: Interpreters and compilers are two
Page 21 and 22: Inside the 8052-BASIC 2 Inside the
Page 23 and 24: Inside the 8052-BASIC • You can a
Page 25 and 26: hardware manuals. For programming,
Page 27 and 28: Inside the 8052-BASIC Figure 2-2 Pi
Page 29 and 30: Inside the 8052-BASIC Table 2-2. (p
Page 31 and 32: Inside the 8052-BASIC Code and data
Page 33 and 34: Powering Up 3 Powering Up This chap
Page 35 and 36: Powering Up Table 3-1. Parts list f
Page 37 and 38: Powering Up Figure 3-2. Truth table
Page 39 and 40: Powering Up Jumper J3 chooses the c
Page 41 and 42: Powering Up Figure 3-3. This is the
Page 43 and 44: Powering Up Construction Tips These
Page 45 and 46: Powering Up Serial Connectors Conne
Page 47 and 48: You’re now ready to power up the
Page 49 and 50: Powering Up PRINT XTAL Line Editing
Page 51 and 52: Powering Up PORT 1 Bit Values: Bit
Page 53 and 54: Powering Up Listing 3-3. Allows use
Page 55 and 56: 10 CLOCK 1:TIME=0:SEC=0 20 A=0 30 P
Page 57: Saving Programs 4 Saving Programs I
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
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The 82C55 also has CMOS-compatible
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Inputs and Outputs Pin Symbol Input
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Inputs and Outputs An 8255 Interfac
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Inputs and Outputs XBY(0FC03h)=9BH
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To set or clear a different bit, de
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Switches and Keypads 7 Switches and
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Switches and Keypads Figure 7-2. Us
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exact value depending on the switch
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Switches and Keypads Figure 7-4. Tw
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Switches and Keypads Figure 7-6. A
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Switches and Keypads Custom Keypads
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Switches and Keypads • A single c
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Switches and Keypads Listing 7-3. T
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Displays 8 Displays In addition to
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Displays Figure 8-1. LED interfaces
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Displays Figure 8-2. Ways to connec
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Displays Figure 8-4. Four output po
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Displays Figure 8-5. The ICM7218D c
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In Figure 8-5’s circuit, an 82(C)
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Displays Figure 8-7. With the TC721
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Displays Figure 8-8. With a charact
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Table 8-1. LCD modules containing t
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Each character in the CG ROM and CG
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Displays Interfacing Full control o
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Displays Listing 8-4 (page 2 0f 2).
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Displays Listing 8-5. Displays key
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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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