The Microcontroller Idea Book - Jan Axelson's Lakeview Research

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Chapter 10 To generate an interrupt at a specific time, you select an alarm frequency by setting or clearing three mask bits (bit 7 of registers 3, 5, and 7), and storing the desired alarm data in bits 0-6 of the same registers. Clearing a register’s mask bit means that the DS1286 will use values in that register to determine the alarm frequency. Setting a mask bit means that the DS1286 will ignore the information in the register. For example, to generate an interrupt at 3:15 daily, you would store the following values: Register Mask Byte Alarm Data 3 0001 0101 15 minutes 5 0000 0011 3 hours 7 1XXX XXXX days (X=don’t care) Table 10-3. Decimal numbers and their equivalents in binary and binary-coded decimal. The values 0-9 are identical in BCD and binary. Decimal Binary-coded Decimal (BCD) Binary 0 0000 0000 0000 0000 1 0000 0001 0000 0001 2 0000 0010 0000 0010 3 0000 0011 0000 0011 4 0000 0100 0000 0100 5 0000 0101 0000 0101 6 0000 0110 0000 0110 7 0000 0111 0000 0111 8 0000 1000 0000 1000 9 0000 1001 0000 1001 10 0001 0000 0000 1010 11 0001 0001 0000 1011 19 0001 1001 0001 0011 20 0010 0000 0001 0100 29 0010 1001 0001 1101 30 0011 0000 0001 1110 99 1001 1001 0110 0011 178 The Microcontroller Idea Book
If you want an alarm frequency other than daily, hourly, or on the minute, there are a couple of ways to achieve it. For an alarm every 10 minutes, you could generate an interrupt once per minute and ignore 9 out of 10 interrupts. If this seems wasteful, you can update the alarm minutes to the next desired value after each interrupt. Using the example of an interrupt every 10 minutes, you would set the mask bits for when minutes match (0-1-1), and start out by storing 0 in register 3, which will cause an interrupt to occur on the hour. When the interrupt occurs, you would add 10 to register 3 to schedule the next interrupt for 10 minutes after the hour. By continuing to add 10 to register 3 after each interrupt, and returning to 0 on a count of 60, you end up with an interrupt every 10 minutes. As Table 10-1 shows, many of the DS1286’s registers have multiple functions. In register 9, bits 0-4 store the current month, bit 6 enables the square-wave output, bit 7 enables the clock, and bit 5 is always 0. For situations like this, you can create mask bytes and use BASIC-52’s logical operators to read and write to selected bits while ignoring other bits in a register. For example, assume that you want to store a month in bits 0-4 of the 1286’s register 9, without affecting the settings of bits 5-7. To do so, follow these steps: (1) Read the current value of the byte. In our example, with a current month of December, the clock enabled, and the square wave disabled, register 9 will hold these values: 0101 0010 (2) Create a mask byte by setting all bits to be masked, or unchanged, to 1, and clearing the other bits. To alter only the month’s value, bits 5-7 are masked: 1110 0000 (3) Logically AND the current value with the mask byte, with this result: 0100 0000 (4) Place the new month’s value in bits 0-4 of the byte. To change the month to June (6th month), logically OR the above byte with this: 0000 0110 which results in: 0100 0110 Clocks and Calendars The Microcontroller Idea Book 179
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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
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Inputs and Outputs 6 Inputs and Out
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Unassigned space remains in the mem
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U11 is a 74HCT138 3-to-8-line decod
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If you wish, you can wire U14’s i
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Inputs and Outputs Figure 6-4. Outp
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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
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
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: Clocks and Calendars Table 10-1. Re
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
Page 199 and 200: Control Circuits Listing 11-1. Cont
Page 201 and 202: Control Circuits Listing 11-2. Demo
Page 203 and 204: Control Circuits disables the outpu
Page 209 and 210: Wireless Links 12 Wireless Links Wi
Page 211 and 212: Wireless Links Figure 12-2. This in
Page 213 and 214: Wireless Links Because there are th
Page 215 and 216: Wireless Links Figure 12-4. The GP1
Page 217 and 218: through the LEDs. If you prefer an
Page 219 and 220: Wireless Links Figure 12-6. Using a
Page 221 and 222: Wireless Links Figure 12-7. Using a
Page 223 and 224: Wireless Links IREDs emit energy at
Page 225 and 226: In the infrared link, the amount of
Page 227 and 228: Calling Assembly-language Routines
Page 229 and 230: into memory in the 8052-BASIC syste
Page 231 and 232: 2048h in code memory. This is becau
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Page 235 and 236: Successful assembly is a good sign,
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Calling Assembly-language Routines
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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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